diff --git a/src/main/java/de/thm/arsnova/service/ContentFindQueryService.java b/src/main/java/de/thm/arsnova/service/ContentFindQueryService.java
index ad668a81f3f7903fe2724dc8e66abfcaaf81f235..c1df6a20ebf2b699ec266c06b4de4b64cf3462ee 100644
--- a/src/main/java/de/thm/arsnova/service/ContentFindQueryService.java
+++ b/src/main/java/de/thm/arsnova/service/ContentFindQueryService.java
@@ -21,6 +21,7 @@ package de.thm.arsnova.service;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 import org.springframework.stereotype.Service;
 
 import de.thm.arsnova.model.Content;
@@ -30,15 +31,28 @@ import de.thm.arsnova.model.FindQuery;
 public class ContentFindQueryService implements FindQueryService<Content> {
 	private RoomService roomService;
 	private ContentService contentService;
+	private ContentGroupService contentGroupService;
 
-	public ContentFindQueryService(final RoomService roomService, final ContentService contentService) {
+	public ContentFindQueryService(final RoomService roomService, final ContentService contentService,
+			final ContentGroupService contentGroupService) {
 		this.roomService = roomService;
 		this.contentService = contentService;
+		this.contentGroupService = contentGroupService;
 	}
 
 	@Override
 	public Set<String> resolveQuery(final FindQuery<Content> findQuery) {
 		final Set<String> contentIds = new HashSet<>();
+
+		if (findQuery.getExternalFilters().get("notInContentGroupOfRoomId") instanceof String) {
+			final String roomId = (String) findQuery.getExternalFilters().get("notInContentGroupOfRoomId");
+			final Set<String> idsWithGroup = contentGroupService.getByRoomId(roomId).stream()
+					.flatMap(cg -> cg.getContentIds().stream()).collect(Collectors.toSet());
+			final Set<String> idsWithoutGroup = contentService.getByRoomId(roomId).stream()
+					.map(Content::getId).filter(id -> !idsWithGroup.contains(id)).collect(Collectors.toSet());
+			contentIds.addAll(idsWithoutGroup);
+		}
+
 		if (findQuery.getProperties().getRoomId() != null) {
 			final List<Content> contentList = contentService.getByRoomId(findQuery.getProperties().getRoomId());
 			for (final Content c : contentList) {