Attention deficit hyperactivity disorder has nothing to do with intelligence or IQ. If 2% of the general population are eligible for Mensa, then 2% of the ADHD population are eligible for Mensa. There is a difference between having knowledge and having the ability to apply knowledge. Those with ADHD know what to do; they struggle doing what they know to do.
Often, ADHD and high intelligence present added challenges for those with ADHD. Because of their intelligence, many have higher expectations of performance. If you are not aware of these challenges, it is hard to manage them. I encourage you to take the time to listen to my insightful interview with Dr. Thomas E. Brown to understand this dynamic and the reality that those with ADHD know what to do. Their challenge is in executing what they know to do.