To reproduce: add a RadCollapsiblePanel and a RadListView inside it. Make the RadListView considerably smaller than the panel and place it at the center of the container. Set the ContentSizingMode property to CollapsiblePanelContentSizingMode.FitToContentWidth | CollapsiblePanelContentSizingMode.FitToContentHeight. When you run the application, you will see that the RadCollapsiblePanel does not have the same size as the RadListView. It is sized only from the right and down corners, although there are undesired margins as well.