Unfortunately, many people, including many psychotherapists, mistakenly think that Obsessive-compulsive disorder (OCD) in children and adolescents is rare. Recent research indicates that approximately half of all adults with OCD experience clinical symptoms of the disorder during their childhood. OCD in childhood is a chronic and distressing disorder that can lead to severe impairments in social, academic, and family functioning. Epidemiologic studies suggest that OCD is as common among children as adults, with a lifetime prevalence of 2% to 4% and a 6-month prevalence of 0.5% to YO. Clinic-based studies suggest a mean age of onset for childhood OCD from 6 to 11 years of age, 36 which is bimodally distributed with peaks in early childhood and early adolescence. As true for adult patients with the disorder, obsessions without compulsions were relatively rare, multiple rituals were common, and the most common compulsive ritual was washing. Comorbid anxiety disorders were common among the children, but depressive disorders were rare. OCD is defined by the presence of obsessive thoughts or acts and/or compulsive behaviours. This is a disorder that may begin in either childhood or adulthood, and may manifest in a number of different ways. According to the diagnostic criteria for OCD outlined by DSM-IV (American Psychiatric Association, 1994), obsessions are characterized as recurrent, persistent and irrational impulses, thoughts or images that cause marked anxiety or distress and are not just excessive worries of real-life problems. On the other hand, compulsions can be defined as ritualistic, repetitive and purposeful behaviours (e.g., checking) or mental acts (e.g., counting) that an individual feels obliged to perform in response to an obsession. The purpose of ritualistic behaviours or mental acts is to prevent or reduce marked distress, to neutralize obsessional thoughts or to prevent some dreaded event or situation. Biological factors (e.g., genetics) may play a prominent role in the development of the early-onset subtype.