Sometimes children who are very intelligent (referred to as gifted) can be diagnosed incorrectly with ADD or ADHD.
How could this happen?
A gifted child may be under challenged and bored in the classroom. When not stimulated enough, they can feel that it’s not worth paying attention and applying themselves.
It is generally best for kids and teens with the ADD or ADHD diagnosis to get a full psychoeducational assessment. This is testing for intelligence (IQ) as well as academic achievement. This would show if in fact your child is gifted or not.
Sorting out this issue can be complicated, and a new book has come out which discusses this in detail. If you are concerned that this situation may apply to you or your child, consider this great resource.