diff --git a/src/components/EditableChipList.vue b/src/components/EditableChipList.vue
index 3411863a..59786107 100644
--- a/src/components/EditableChipList.vue
+++ b/src/components/EditableChipList.vue
@@ -26,7 +26,7 @@ const props = withDefaults(
 const itemsToRender = computed(() =>
   props.items.map((item) => ({
     key: item[props.itemKey] as string | number | symbol,
-    title: item[props.itemTitle],
+    title: item[props.itemTitle] as string | undefined,
   }))
 );
 </script>
@@ -47,7 +47,11 @@ const itemsToRender = computed(() =>
             @click="toggle"
           >
             <slot name="item-prepend" :key="key" :item="items[idx]"></slot>
-            <span class="overflow-hidden">{{ title }}</span>
+            <v-tooltip :text="title" location="end">
+              <template #activator="{ props }">
+                <span v-bind="props" class="text-truncate">{{ title }}</span>
+              </template>
+            </v-tooltip>
             <v-spacer />
             <slot name="item-append" :key="key" :item="items[idx]"></slot>
           </v-chip>
diff --git a/src/components/SegmentGroupControls.vue b/src/components/SegmentGroupControls.vue
index 8f1f0dd9..fd8604ef 100644
--- a/src/components/SegmentGroupControls.vue
+++ b/src/components/SegmentGroupControls.vue
@@ -48,7 +48,7 @@ const currentSegmentGroups = computed(() => {
 const paintStore = usePaintToolStore();
 const currentSegmentGroupID = computed({
   get: () => paintStore.activeSegmentGroupID,
-  set: (id) => paintStore.setActiveLabelmap(id),
+  set: (id) => paintStore.setActiveSegmentGroup(id),
 });
 
 // clear selection if we delete the active segment group
@@ -204,6 +204,11 @@ function openSaveDialog(id: string) {
       </v-menu>
     </div>
     <v-divider />
+
+    <segment-group-opacity
+      v-if="currentSegmentGroupID"
+      :group-id="currentSegmentGroupID"
+    />
     <v-radio-group
       v-model="currentSegmentGroupID"
       hide-details
@@ -258,10 +263,6 @@ function openSaveDialog(id: string) {
     <v-divider />
   </div>
   <div v-else class="text-center text-caption">No selected image</div>
-  <segment-group-opacity
-    v-if="currentSegmentGroupID"
-    :group-id="currentSegmentGroupID"
-  />
   <segment-list
     v-if="currentSegmentGroupID"
     :group-id="currentSegmentGroupID"
diff --git a/src/components/SegmentGroupOpacity.vue b/src/components/SegmentGroupOpacity.vue
index 695f3981..63c3bdbd 100644
--- a/src/components/SegmentGroupOpacity.vue
+++ b/src/components/SegmentGroupOpacity.vue
@@ -25,7 +25,7 @@ const setOpacity = (opacity: number) => {
 
 <template>
   <v-slider
-    class="pa-4"
+    class="ma-4"
     label="Segment Group Opacity"
     min="0"
     max="1"
diff --git a/src/components/SegmentList.vue b/src/components/SegmentList.vue
index d303bd41..640e1e28 100644
--- a/src/components/SegmentList.vue
+++ b/src/components/SegmentList.vue
@@ -11,6 +11,7 @@ import { hexaToRGBA, rgbaToHexa } from '@/src/utils/color';
 import { reactive, ref, toRefs, computed, watch } from 'vue';
 import { SegmentMask } from '@/src/types/segment';
 import { usePaintToolStore } from '@/src/store/tools/paint';
+import { RGBAColor } from '@kitware/vtk.js/types';
 
 const props = defineProps({
   groupId: {
@@ -57,6 +58,58 @@ watch(
   { immediate: true }
 );
 
+// --- segment opacity --- //
+
+const selectedSegmentMask = computed(() => {
+  if (!selectedSegment.value) return null;
+  return segmentGroupStore.getSegment(groupId.value, selectedSegment.value);
+});
+
+const segmentOpacity = computed(() => {
+  if (!selectedSegmentMask.value) return 1;
+  return selectedSegmentMask.value.color[3] / 255;
+});
+
+const setSegmentOpacity = (opacity: number) => {
+  if (!selectedSegmentMask.value) {
+    return;
+  }
+
+  const color = selectedSegmentMask.value.color;
+  segmentGroupStore.updateSegment(
+    groupId.value,
+    selectedSegmentMask.value.value,
+    {
+      color: [
+        ...(color.slice(0, 3) as [number, number, number]),
+        Math.round(opacity * 255),
+      ],
+    }
+  );
+};
+
+const toggleVisible = (value: number) => {
+  const segment = segmentGroupStore.getSegment(groupId.value, value);
+  if (!segment) return;
+  segmentGroupStore.updateSegment(groupId.value, value, {
+    visible: !segment.visible,
+  });
+};
+
+const allVisible = computed(() => {
+  return segments.value.every((seg) => seg.visible);
+});
+
+function toggleGlobalVisible() {
+  const visible = !allVisible.value;
+
+  segments.value.forEach((seg) => {
+    segmentGroupStore.updateSegment(groupId.value, seg.value, {
+      visible,
+    });
+  });
+}
+
 // --- editing state --- //
 
 const editingSegmentValue = ref<Maybe<number>>(null);
@@ -106,6 +159,30 @@ function deleteEditingSegment() {
 </script>
 
 <template>
+  <v-btn @click.stop="toggleGlobalVisible">
+    Toggle Segments
+    <slot name="append">
+      <v-icon v-if="allVisible" class="pl-2">mdi-eye</v-icon>
+      <v-icon v-else class="pl-2">mdi-eye-off</v-icon>
+      <v-tooltip location="top" activator="parent">{{
+        allVisible ? 'Hide' : 'Show'
+      }}</v-tooltip>
+    </slot>
+  </v-btn>
+
+  <v-slider
+    class="ma-4"
+    label="Segment Opacity"
+    min="0"
+    max="1"
+    step="0.01"
+    density="compact"
+    hide-details
+    thumb-label
+    :model-value="segmentOpacity"
+    @update:model-value="setSegmentOpacity($event)"
+  />
+
   <editable-chip-list
     v-model="selectedSegment"
     :items="segments"
@@ -119,11 +196,27 @@ function deleteEditingSegment() {
       <div class="dot-container mr-3">
         <div
           class="color-dot"
-          :style="{ background: rgbaToHexa(item.color) }"
+          :style="{ background: rgbaToHexa([...item.color.slice(0,3), 255] as RGBAColor) }"
         />
       </div>
     </template>
-    <template #item-append="{ key }">
+    <template #item-append="{ key, item }">
+      <v-btn
+        icon
+        size="small"
+        density="compact"
+        class="ml-auto mr-1"
+        variant="plain"
+        @click.stop="toggleVisible(key as number)"
+      >
+        <v-icon v-if="item.visible" style="pointer-events: none"
+          >mdi-eye</v-icon
+        >
+        <v-icon v-else style="pointer-events: none">mdi-eye-off</v-icon>
+        <v-tooltip location="left" activator="parent">{{
+          item.visible ? 'Hide' : 'Show'
+        }}</v-tooltip>
+      </v-btn>
       <v-btn
         icon="mdi-pencil"
         size="small"
diff --git a/src/components/vtk/VtkSegmentationSliceRepresentation.vue b/src/components/vtk/VtkSegmentationSliceRepresentation.vue
index 5a5a1d45..0ba1db0f 100644
--- a/src/components/vtk/VtkSegmentationSliceRepresentation.vue
+++ b/src/components/vtk/VtkSegmentationSliceRepresentation.vue
@@ -117,7 +117,7 @@ const applySegmentColoring = () => {
     const r = segment.color[0] || 0;
     const g = segment.color[1] || 0;
     const b = segment.color[2] || 0;
-    const a = segment.color[3] || 0;
+    const a = (segment.visible && segment.color[3]) || 0;
     cfun.addRGBPoint(segment.value, r / 255, g / 255, b / 255);
     ofun.addPoint(segment.value, a / 255);
 
diff --git a/src/config.ts b/src/config.ts
index f2cc18ab..420f4948 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -178,6 +178,7 @@ export const Layouts: Record<string, Layout> = [
 ].reduce((layouts, layout) => {
   return { ...layouts, [layout.name]: layout };
 }, {});
+
 export const SAMPLE_DATA: SampleDataset[] = [
   {
     name: 'CTA Head and Neck',
diff --git a/src/io/state-file/schema.ts b/src/io/state-file/schema.ts
index b4abb7af..e251f7ac 100644
--- a/src/io/state-file/schema.ts
+++ b/src/io/state-file/schema.ts
@@ -240,6 +240,7 @@ const SegmentMask = z.object({
   value: z.number(),
   name: z.string(),
   color: RGBAColor,
+  visible: z.boolean().default(true),
 });
 
 export const SegmentGroupMetadata = z.object({
diff --git a/src/store/segmentGroups.ts b/src/store/segmentGroups.ts
index f71193e0..4b7ded20 100644
--- a/src/store/segmentGroups.ts
+++ b/src/store/segmentGroups.ts
@@ -223,6 +223,7 @@ export const useSegmentGroupStore = defineStore('segmentGroup', () => {
           value: segment.labelID,
           name: segment.SegmentLabel,
           color: [...segment.recommendedDisplayRGBValue, 255],
+          visible: true,
         }));
       }
     }
@@ -237,6 +238,7 @@ export const useSegmentGroupStore = defineStore('segmentGroup', () => {
       value,
       name: makeDefaultSegmentName(value),
       color: getNextColor(),
+      visible: true,
     }));
   }
 
@@ -327,6 +329,7 @@ export const useSegmentGroupStore = defineStore('segmentGroup', () => {
       name: makeDefaultSegmentName(value),
       value,
       color: DEFAULT_SEGMENT_COLOR,
+      visible: true,
     };
   }
 
diff --git a/src/store/tools/paint.ts b/src/store/tools/paint.ts
index e640201d..6fc74b7d 100644
--- a/src/store/tools/paint.ts
+++ b/src/store/tools/paint.ts
@@ -1,7 +1,7 @@
 import type { Vector2 } from '@kitware/vtk.js/types';
 import { useCurrentImage } from '@/src/composables/useCurrentImage';
 import { Manifest, StateFile } from '@/src/io/state-file/schema';
-import { computed, ref, watch } from 'vue';
+import { computed, ref, watchEffect } from 'vue';
 import { vec3 } from 'gl-matrix';
 import { defineStore } from 'pinia';
 import { Maybe } from '@/src/types';
@@ -27,9 +27,10 @@ export const usePaintToolStore = defineStore('paint', () => {
     return this.$paint.factory;
   }
 
+  const segmentGroupStore = useSegmentGroupStore();
+
   const activeLabelmap = computed(() => {
     if (!activeSegmentGroupID.value) return null;
-    const segmentGroupStore = useSegmentGroupStore();
     return segmentGroupStore.dataIndex[activeSegmentGroupID.value] ?? null;
   });
 
@@ -47,25 +48,37 @@ export const usePaintToolStore = defineStore('paint', () => {
   /**
    * Sets the active labelmap.
    */
-  function setActiveLabelmap(segmentGroupID: Maybe<string>) {
+  function setActiveSegmentGroup(segmentGroupID: Maybe<string>) {
     activeSegmentGroupID.value = segmentGroupID;
   }
 
+  /**
+   * Gets the first segment group ID for a given image.
+   * @param imageID
+   */
+  function getFirstSegmentGroupID(imageID: Maybe<string>): Maybe<string> {
+    if (!imageID) return null;
+    const segmentGroups = segmentGroupStore.orderByParent[imageID];
+    if (segmentGroups && segmentGroups.length > 0) {
+      return segmentGroups[0];
+    }
+    return null;
+  }
+
   /**
    * Sets the active labelmap from a given image.
    *
    * If a labelmap exists, pick the first one. If no labelmap exists, create one.
    */
-  function setActiveLabelmapFromImage(imageID: Maybe<string>) {
+  function ensureActiveSegmentGroupForImage(imageID: Maybe<string>) {
     if (!imageID) {
-      setActiveLabelmap(null);
+      setActiveSegmentGroup(null);
       return;
     }
 
-    const segmentGroupStore = useSegmentGroupStore();
-    const labelmaps = segmentGroupStore.orderByParent[imageID];
-    if (labelmaps?.length) {
-      activeSegmentGroupID.value = labelmaps[0];
+    const segmentGroupID = getFirstSegmentGroupID(imageID);
+    if (segmentGroupID) {
+      setActiveSegmentGroup(segmentGroupID);
     } else {
       activeSegmentGroupID.value =
         segmentGroupStore.newLabelmapFromImage(imageID);
@@ -83,7 +96,6 @@ export const usePaintToolStore = defineStore('paint', () => {
       if (!activeSegmentGroupID.value)
         throw new Error('Cannot set active segment without a labelmap');
 
-      const segmentGroupStore = useSegmentGroupStore();
       const { segments } =
         segmentGroupStore.metadataByID[activeSegmentGroupID.value];
 
@@ -158,7 +170,7 @@ export const usePaintToolStore = defineStore('paint', () => {
     if (!imageID) {
       return false;
     }
-    setActiveLabelmapFromImage(imageID);
+    ensureActiveSegmentGroupForImage(imageID);
     this.$paint.setBrushSize(this.brushSize);
 
     isActive.value = true;
@@ -190,22 +202,26 @@ export const usePaintToolStore = defineStore('paint', () => {
     if (paint.activeSegmentGroupID !== null) {
       activeSegmentGroupID.value =
         segmentGroupIDMap[paint.activeSegmentGroupID];
-      setActiveLabelmap(activeSegmentGroupID.value);
+      setActiveSegmentGroup(activeSegmentGroupID.value);
       setActiveSegment.call(this, paint.activeSegment);
     }
   }
 
-  // --- change labelmap if paint is active --- //
+  // Create segment group if paint is active and none exist.
+  // If paint is not active, but there is a segment group for the current image, set it as active.
+  watchEffect(() => {
+    const imageID = currentImageID.value;
+    if (!imageID) return;
 
-  watch(
-    currentImageID,
-    (imageID) => {
-      if (isActive.value) {
-        setActiveLabelmapFromImage(imageID);
+    if (isActive.value) {
+      ensureActiveSegmentGroupForImage(imageID);
+    } else {
+      const segmentGroupID = getFirstSegmentGroupID(imageID);
+      if (segmentGroupID) {
+        setActiveSegmentGroup(segmentGroupID);
       }
-    },
-    { immediate: true }
-  );
+    }
+  });
 
   return {
     // state
@@ -222,8 +238,8 @@ export const usePaintToolStore = defineStore('paint', () => {
     deactivateTool,
 
     setMode,
-    setActiveLabelmap,
-    setActiveLabelmapFromImage,
+    setActiveSegmentGroup,
+    ensureActiveSegmentGroupForImage,
     setActiveSegment,
     setBrushSize,
     setSliceAxis,
diff --git a/src/types/segment.ts b/src/types/segment.ts
index dacfb907..6db17d61 100644
--- a/src/types/segment.ts
+++ b/src/types/segment.ts
@@ -4,4 +4,5 @@ export interface SegmentMask {
   value: number;
   name: string;
   color: RGBAColor;
+  visible: boolean;
 }