The focusing on video games and the like is not a sign a child does not have ADD. There are many different types. The problem seems to be with things they are not interested in. There is a test called a TOVA test which is done on a computer. The kids with ADD/ADHD stay as focused as those without. It is the time response that seems to be the biggest difference. From what I have read is seems to be so boring anyone could get distracted, but those with ADD/ADHD really can not stay focused on the task at hand.
I believe thats one of the test they will be giving my son along with some others.