ADHD is a complex disorder of impairment of brain functions, which burdens our society with significant financial costs. Its salient features are inattention, hyperactivity, and impulsivity. In many cases, it is accompanied by one or more serious psychiatric comorbidities. Criteria for its diagnosis have emerged over the past four decades, resulting in better recognition and more widespread treatment. The current opinion estimates its prevalence in the USA to be 5 – 10% among school-aged children. It has strong heritability and genetic links, as well as environmental predispositions and triggers. Although it mostly affects school-aged children, it is well known to affect preschoolers, youths, and even adults, with distinct manifestations and progression. Treatment predominantly relies on prescribing stimulant medications (amphetamines), of which methylphenidate is the most widely used. Psychosocial therapy has an important but less distinguished role in the management of the disorder.