>>You can use Node properties Parent, Child, Root, etc., so true value for
>>ISNULL(thisform.myOleTree.SelectedItem.Parent)
>>or
>>ISNULL(thisform.myOleTree.Nodes(1).Parent)
>>means that it is a root node.
>
>So, if I have 3 items which are starting a root, SelectedItem.Parent will returns .T. for them.

Actually, no.
SelectedItem.Parent is an object, and it has the same properties as SelectedItem (like SelectedItem.Parent.Key), so better to check ISNULL(thisform.myOleTree.SelectedItem.Parent)
or
IF TYPE(thisform.myOleTree.SelectedItem.Parent)="O"