We did a QEEG...which was wires or something similar attached to his head. If we are talking about the same type of test I feel this is pretty thorough after seeing the results and discussing them with the psychiatrist. I was much more comfortable going with these results rather than just a verbal "yes he is " type of diagnosis.
My ex also has had a QEEG done by a neurologist. From best I can tell these are pretty thorough and informative.
FYI: our doctor also recommended a 6 hour glucose tolerance test for our son in conjunction to the QEEG. We discovered that he has reactive hypoglycemia. Which can trigger some of the same behaviors found with ad/hd.