We don't have any first hand experience with gifted testing, but I do know that in my state there is a list published by the Dept of Education of what tests are accepted and what scores are needed to qualify.
We do have experience with IQ testing, since the IEP team strongly insisted on it for DS's most recent triennial evaluation. I was able to put it off for about 5 years, then finally we were at a point where I felt that IQ testing would give some good information.
We knew that testing would be a challenge. Traditional IQ tests are language based and DS has language processing difficulties due to his autism. Non-verbal IQ tests are visually based and DS has mild visual impairments. They don't really make tests for kids like my DS. I agreed to have testing done only if our private psychologist did the testing. She's the head of the psychology department at the Children's Hospital and she has worked with DS since he was 3; she was part of his diagnostic team. I was not going to trust a school psychologist who DS does not know to administer an IQ test, although I did allow her to conduct his achievement testing.
Our psychologist took all of DS's issues into account when administering his test. She gave him positive rewards (train stickers) for completing each subsection and cooperating. She gave him breaks between subsections. She made sure the room was free of glare and accommodated his sensory needs. She let him be physically active (pace) while verbally answering questions.
DS had the WISC-IV (which PP mentioned above) as well as the Leiter Nonverbal IQ Test. Both test gave us some good information. DS's subtest scatter was huge, which makes his Full Scale IQ Score unreliable, but we got a really good snapshot of where he does well and where he struggles.
So yes, in your situation I would look for someone who is experienced in administering the test to kids with ADHD. And make sure you have a thorough understanding of all the subtest score. I know it's tempting to just look at the overall composite score, especially since you want the test to qualify for the gifted program. But the subtest scores can give you a lot of information that can impact his schooling.
Gena
DS, age 11 and always amazing
“Autistics are the ultimate square pegs, and the problem with pounding a square peg into a round hole is not that the hammering is hard work. It's that you're destroying the peg." - Paul Collins, Not Even Wrong