Attention deficit hyperactivity disorder (ADHD) is a neuropsychiatric functional impairment that manifests in childhood. The symptoms include attention deficits, impulsivity, and hyperactivity, and the functional impairment usually remains throughout life. However, the degree and type of symptoms as well as long-term outcome varies greatly among individuals. It is estimated that between three to ten percent of all school age children suffer from ADHD. Boys are overrepresented but more and more girls are also diagnosed. In adults, the prevalence is estimated to be between three and four percent. Knowledge on genetic factors, neurobiological processes, and cognitive functions linked to ADHD has increased greatly. However, the mechanisms linking such observations together remain unclear. We are collecting data on individuals with ADHD to broadly study disease mechanisms, prognostic markers and potential novel treatment rationales.