Polly ADHD was explained to me as not the inability to pay attention, but the inability to CHOOSE to pay attention to something necessary but boring. Sure he may be able to read or play computer games for hours, but he may be literally unable to make him self focus on hand writing, or keep focused on getting dressed when he can see the Lego, for example. The question is how age appropriate is his level of distraction. Particularly if he is noticing more input than the average child of his age.