It was thought that obsessive compulsive disorder (OCD) in children was a rare disorder. But most of the research conducted during the last 10 years found that the prevalence rate is up to 3%, and that OCD rates in children and adults are the same. It was also found that one-third to one-half of adult subjects experience the onset of OCD in childhood and adolescence. The aim of this review is to focus on various information available in the literature about OCD in children and adolescents. The main focus is on its epidemiology, phenomenology, aetiology and various treatment methods.