The etiological factors of „attention deficit hyperactivity disorder“ (ADHD) are multiple and have an importance that vary according to the individual. Nevertheless, the current state of knowledge suggests a significant biological component to the pathophysiology of this problem, and a genetic influence in particular. It thus seems that ADHD is essentially characterized by it’s dimension of impulsivity, linked to a defect of inhibitor control, specifically implying certain cerebral structures as well as a dysfunction of the cathecolaminergic system, and in particular, the dopaminergic system. Certainly, environmental factors influence the symptomatology and expression of the problem, but it is noted that ADHD itself influences these factors.