diff --git a/internal/domain/list.go b/internal/domain/list.go
index 904f070..99acd38 100644
--- a/internal/domain/list.go
+++ b/internal/domain/list.go
@@ -49,3 +49,47 @@ func (s *ListService) Create(ctx context.Context, name string, userIDs []string)
 
 	return s.repo.CreateList(ctx, name, userIDs)
 }
+
+func (s *ListService) AddUserToList(ctx context.Context, listID string, userID string) error {
+	if listID == "" {
+		return errors.New("list id must not be empty")
+	}
+	if userID == "" {
+		return errors.New("user id must not be empty")
+	}
+
+	return s.repo.AddUserToList(ctx, listID, userID)
+}
+
+func (s *ListService) RemoveUserFromList(ctx context.Context, listID string, userID string) error {
+	if listID == "" {
+		return errors.New("list id must not be empty")
+	}
+	if userID == "" {
+		return errors.New("user id must not be empty")
+	}
+
+	return s.repo.RemoveUserFromList(ctx, listID, userID)
+}
+
+func (s *ListService) CreateListItem(ctx context.Context, listID string, title string) (*ListItem, error) {
+	if listID == "" {
+		return nil, errors.New("list id must not be empty")
+	}
+	if title == "" {
+		return nil, errors.New("list item title must not be empty")
+	}
+
+	return s.repo.CreateListItem(ctx, listID, title)
+}
+
+func (s *ListService) UpdateListItem(ctx context.Context, listItemID, title string, isCompleted bool) error {
+	if listItemID == "" {
+		return errors.New("list item id must not be empty")
+	}
+	if title == "" {
+		return errors.New("list item title must not be empty")
+	}
+
+	return s.repo.UpdateListItem(ctx, listItemID, title, isCompleted)
+}