The attention deficit hyperactivity disorder (ADHD) is the most common diagnosis in child psychiatry, and persists very often in adulthood. These patients have poor lifestyles, especially in affective, work and social areas. Although patients with ADHD have a high rate of comorbidity (e.g. drug and alcohol abuse, depressive and anxiety disorders), this diagnosis is missed by the general physician, deferring its identification and opportune treatment. This article is a review about this disorder and gives tools for its recognition and derivation (Rev Méd Chile 2003; 131: 1195-201).