ADHD is one of the most common childhood psychiatric disorders, affecting about 5% of all school-age children worldwide (Polanczyk et al. 2007). ADHD is characterised by clinically significant levels of impulsive, hyperactive and inattentive behaviors. Whilst ADHD is classified as a childhood disorder, a large proportion of individuals will continue to exhibit symptoms into adolescence and adulthood. The impulsive behaviors of children with ADHD, in particular, place them at manifold increased risk for various adverse consequences: they are at a 5-fold increased risk for comorbid oppositional and antisocial behavior disorders, and a 3-fold increased risk for all forms of substance use (smoking, use of marihuana, cocaine and other substances) and behavioral addictions (gambling) from early adolescence onward, as well as an earlier onset of substance misuse (Biederman et al. 1997).