I found your snapshot very strange. It seems like the DefaultImageSrc property of the RadTreeViewItem is used and a blank / transparent image is used. This problem cannot be caused by the CheckBox element from the Template of the RadTreeViewItem, when it is not used, there is no reserved space. You can examine this is the attached project. The first RadTreeViewItem has Image and Checkbox, the second has only Image, the third has only Checkbox and the fourth has no image and no checkbox.
Is it possible for you to send us your XAML or a runnable sample showing how this RadTreeViewItem is produced? This will be highly appreciated and we would be better able to assist you. Thank you in advance.
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>