diff --git a/app/src/main/java/io/timelimit/android/ui/manage/category/apps/add/AddCategoryAppsFragment.kt b/app/src/main/java/io/timelimit/android/ui/manage/category/apps/add/AddCategoryAppsFragment.kt
index 96772f7..8a6be7d 100644
--- a/app/src/main/java/io/timelimit/android/ui/manage/category/apps/add/AddCategoryAppsFragment.kt
+++ b/app/src/main/java/io/timelimit/android/ui/manage/category/apps/add/AddCategoryAppsFragment.kt
@@ -22,6 +22,7 @@ import android.view.LayoutInflater
 import androidx.appcompat.app.AlertDialog
 import androidx.fragment.app.DialogFragment
 import androidx.fragment.app.FragmentManager
+import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.Observer
 import androidx.recyclerview.widget.LinearLayoutManager
 import io.timelimit.android.R
@@ -29,9 +30,7 @@ import io.timelimit.android.data.Database
 import io.timelimit.android.data.model.UserType
 import io.timelimit.android.databinding.FragmentAddCategoryAppsBinding
 import io.timelimit.android.extensions.showSafe
-import io.timelimit.android.livedata.map
-import io.timelimit.android.livedata.mergeLiveData
-import io.timelimit.android.livedata.switchMap
+import io.timelimit.android.livedata.*
 import io.timelimit.android.logic.DefaultAppLogic
 import io.timelimit.android.sync.actions.AddCategoryAppsAction
 import io.timelimit.android.ui.main.ActivityViewModel
@@ -80,26 +79,43 @@ class AddCategoryAppsFragment : DialogFragment() {
         val binding = FragmentAddCategoryAppsBinding.inflate(LayoutInflater.from(context))
         val filter = AppFilterView.getFilterLive(binding.filter)
 
+        val showAppsFromOtherCategories = MutableLiveData<Boolean>().apply { value = binding.showOtherCategoriesApps.isChecked }
+        binding.showOtherCategoriesApps.setOnCheckedChangeListener { _, isChecked -> showAppsFromOtherCategories.value = isChecked }
+
         binding.recycler.layoutManager = LinearLayoutManager(context)
         binding.recycler.adapter = adapter
 
-        mergeLiveData(
-                filter,
-                database.app().getApps()
-                        .map { apps -> apps.distinctBy { app -> app.packageName } }
-        ).map {
-            searchTermAndApps ->
+        val childCategories = database.category().getCategoriesByChildId(params.childId)
+        val childCategoriesWithApps = childCategories.switchMap { categories ->
+            database.categoryApp().getCategoryApps(categories.map { it.id })
+                    .map { categoyApps -> categories to categoyApps }
+        }
 
-            val (search, apps) = searchTermAndApps
+        val packageNamesAssignedToOtherCategories = childCategoriesWithApps.map { (_, apps) ->
+            apps.filter { it.categoryId != params.categoryId }.map { it.packageName }.toSet()
+        }.ignoreUnchanged()
 
-            apps?.filter { search?.matches(it) == true }
-        }.map {
-            apps ->
-
-            apps?.sortedBy { app -> app.title.toLowerCase() }
+        filter.switchMap { filter ->
+            database.app().getApps()
+                    .map{ apps -> apps.distinctBy { app -> app.packageName } }
+                    .map { filter to it }
+        }.map { (search, apps) ->
+            apps.filter { search.matches(it) }
+        }.switchMap { apps ->
+            showAppsFromOtherCategories.switchMap { showOtherCategeories ->
+                if (showOtherCategeories) {
+                    liveDataFromValue(apps)
+                } else {
+                    packageNamesAssignedToOtherCategories.map { packagesFromOtherCategories ->
+                        apps.filterNot { packagesFromOtherCategories.contains(it.packageName) }
+                    }
+                }
+            }
+        }.map { apps ->
+            apps.sortedBy { app -> app.title.toLowerCase() }
         }.observe(this, Observer {
             val selectedPackageNames = adapter.selectedApps
-            val visiblePackageNames = it?.map { it.packageName }?.toSet() ?: emptySet()
+            val visiblePackageNames = it.map { it.packageName }.toSet()
             val hiddenSelectedPackageNames = selectedPackageNames.toMutableSet().apply { removeAll(visiblePackageNames) }.size
 
             adapter.data = it
@@ -109,22 +125,18 @@ class AddCategoryAppsFragment : DialogFragment() {
                 resources.getQuantityString(R.plurals.category_apps_add_dialog_hidden_entries, hiddenSelectedPackageNames, hiddenSelectedPackageNames)
         })
 
-        database.category().getCategoriesByChildId(params.childId)
-                .switchMap { categories ->
-                    val categoryById = categories.associateBy { it.id }
+        childCategoriesWithApps.map { (categories, apps) ->
+            val categoryById = categories.associateBy { it.id }
+            val categoryTitleByCategoryId = mutableMapOf<String, String>()
 
-                    database.categoryApp().getCategoryApps(categories.map { it.id }).map { apps ->
-                        val categoryTitleByCategoryId = mutableMapOf<String, String>()
+            apps.forEach {
+                categoryTitleByCategoryId[it.packageName] = categoryById[it.categoryId]?.title ?: ""
+            }
 
-                        apps.forEach {
-                            categoryTitleByCategoryId[it.packageName] = categoryById[it.categoryId]?.title ?: ""
-                        }
-
-                        categoryTitleByCategoryId
-                    }
-                }.observe(this, Observer {
-                    adapter.categoryTitleByPackageName = it
-                })
+            categoryTitleByCategoryId
+        }.observe(this, Observer {
+            adapter.categoryTitleByPackageName = it
+        })
 
         return AlertDialog.Builder(context!!, R.style.AppTheme)
                 .setView(binding.root)
diff --git a/app/src/main/res/layout/fragment_add_category_apps.xml b/app/src/main/res/layout/fragment_add_category_apps.xml
index c5e961b..fda7c5b 100644
--- a/app/src/main/res/layout/fragment_add_category_apps.xml
+++ b/app/src/main/res/layout/fragment_add_category_apps.xml
@@ -40,7 +40,7 @@
             <com.google.android.material.appbar.AppBarLayout
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content">
-                <FrameLayout
+                <LinearLayout
                     android:background="?android:windowBackground"
                     app:layout_scrollFlags="scroll|enterAlways|snap"
                     android:orientation="vertical"
@@ -50,7 +50,14 @@
                     <include android:id="@+id/filter"
                         layout="@layout/app_filter_view" />
 
-                </FrameLayout>
+                    <CheckBox
+                        android:checked="true"
+                        android:id="@+id/show_other_categories_apps"
+                        android:text="@string/category_apps_add_dialog_show_assigned_to_other_category"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content" />
+
+                </LinearLayout>
             </com.google.android.material.appbar.AppBarLayout>
 
             <androidx.recyclerview.widget.RecyclerView
diff --git a/app/src/main/res/values-de/strings-category-apps.xml b/app/src/main/res/values-de/strings-category-apps.xml
index 8937cfd..d956522 100644
--- a/app/src/main/res/values-de/strings-category-apps.xml
+++ b/app/src/main/res/values-de/strings-category-apps.xml
@@ -21,6 +21,7 @@
     <string name="category_apps_add_dialog_filter_hint">Nach Apps suchen</string>
     <string name="category_apps_add_dialog_show_sys_apps">Systemapps anzeigen</string>
     <string name="category_apps_add_dialog_select_all">Alle auswählen</string>
+    <string name="category_apps_add_dialog_show_assigned_to_other_category">Zu anderen Kategorien zugeordnete Apps anzeigen</string>
     <plurals name="category_apps_add_dialog_hidden_entries">
         <item quantity="one">%d ausgeblendeten Eintrag ausgewählt</item>
         <item quantity="other">%s ausgeblendete Einträge ausgewählt</item>
diff --git a/app/src/main/res/values/strings-category-apps.xml b/app/src/main/res/values/strings-category-apps.xml
index 6990d12..73fb5dc 100644
--- a/app/src/main/res/values/strings-category-apps.xml
+++ b/app/src/main/res/values/strings-category-apps.xml
@@ -20,6 +20,7 @@
     <string name="category_apps_add_dialog_btn_positive">Add Apps</string>
     <string name="category_apps_add_dialog_filter_hint">Search Apps</string>
     <string name="category_apps_add_dialog_show_sys_apps">Show system Apps</string>
+    <string name="category_apps_add_dialog_show_assigned_to_other_category">Show Apps assigned to other categories</string>
     <string name="category_apps_add_dialog_select_all">Select all</string>
     <plurals name="category_apps_add_dialog_hidden_entries">
         <item quantity="one">%d hidden entry selected</item>