Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that significantly impacts various aspects of life, including school, work, family, and social relationships. The disorder has a prevalence of 6-7% in children and 4-5% in adults and commonly manifests before the age of 12. Symptoms can be categorised into two groups: attention deficit; and hyperactivity/impulsivity. As individuals age, hyperactivity symptoms generally decrease, while attention deficit symptoms exhibit less change. Attention deficit hyperactivity disorder is associated with numerous adverse outcomes, such as comorbid psychiatric disorders, academic difficulties, accidents, injuries, and increased economic burdens on society and individuals. Children and adults with ADHD have a high rate of psychiatric comorbidity, including learning disorders, autism spectrum disorder, anxiety disorders, mood disorders, tic disorders, adolescent substance abuse, and antisocial personality disorder in adulthood. Timely detection, enhanced intervention strategies, and consistent care may alleviate the clinical and economic burden of ADHD.  Kulcsszavak: ADHD, child and adolescent, adult, comorbidity, economic burden