Since the PFC and dopamine pathways have been hypothesized to play an important role in the pathogenesis of ADHD [9-11,60,61]), we conducted this study in an attempt to test whether the COMT Val108/158Met polymorphism, which is known to be associated with a significant change in the catabolic capacity of this enzyme, modulates the risk for ADHD or various indices of executive control. This evidence concerns the gene COMT and attention deficit-hyperactivity disorder.