The SelectionType property of the Override is not applicable on the Override exposed by individual nodes. You can disable a node altogether by setting its Enabled property to false; this will prevent not only selection but editing and activation as well. If you want to prevent a root node from being selected, you can handle the BeforeSelect event, and cancel it if the Level property is equal to zero. You can also set the UltraTree.Nodes.Override.SelectionType to None, and that will prevent node selection for all nodes in the the root Nodes collection, then set the UltraTree.Override.SelectionType to some other value for nodes at all other levels.