Attention deficit hyperactivity disorder (ADHD) is one of the most common neuropsychiatric disorders in children. ADHD is often chronic persisting into adulthood in about 60% of patients. The disorder is frequently associated with co-occurring disruptive, anxiety, mood and personality disorders as well as substance abuse. The diagnosis of ADHD has to be based on careful assessment of symptoms and impairments in the different phases of life. Recent neuroimaging and genetic data support the neurobiological basis of the disorder. Multimodal treatment options including stimulants, antidepressants and behavioral therapy play a fundamental role in the management of ADHD across the life span.