могу использовать .getElementsByTagName в объекте DOMNodeList? Подобно:

procedure TForm1.selecionarClick(Sender: TObject);
var  DOMDocument: iXMLDOMDocument;
     DOMNodeList: iXMLDOMNodeList;
     DOMNode: iXMLDOMNode;
     DOMElement: iXMLDOMElement;
     i: Integer;
begin
      Memo.Text := '';
      with DOMDocument do
      begin
            DOMDocument := coDOMDocument.Create;
            DOMDocument.load( 'C:\Usuarios.xml' );
            DOMDocument.preserveWhiteSpace := false;
            DOMNodeList := DOMDocument.selectNodes( './/usuario[@codigo="'+codigo.Text+'"]/' );
            for i := 0 to DOMNodeList.length - 1 do
            begin

            end;
      end;
end;

Моя структура XML:

<?xml version="1.0" encoding="utf-8"?>
<usuarios>
    <usuario codigo="1">
           <nome>Name Node</nome>
           <sobrenome>Last Name Node</sobrenome>
           <cidade>City Node</cidade>
           <estado>State Node</estado>
           <email>Mail Node</email>
    </usuario>
</usuarios>