The paper emphasizes the characteristics of ADHD in school children, adolescents, adults, presenting the most important problems occurring during each age. At the same time, the paper presents a study with school population and also with adult population, done in Marmara University. The first study addresses the question of how ADHD symptoms change in course of 2 years in a nonclinical sample, among the sample, who becomes more symptomatic or whose symptoms disappear or lose clinical significance. The second study focuses on the follow-up of the childhood/ adolescent forms of ADHD into youth and later adulthood phases.
Key words: ADHD, school children and adolescent with ADHD, ADHD in adults, comorbidities