Controlled studies show that cognitive behavior therapy (CBT) is an efficacious treatment for young people with obsessive compulsive disorder (OCD). More evidence is needed for effectiveness in clinical settings. We conducted a case note review of 318 patients attending an OCD clinic. Outcomes for 75 patients who received treatment in the clinic were analysed. Following acute treatment, total CYBOCS (Children Yale‐Brown Obsessive Compulsive Scale) score was significantly reduced (22.6 to 10.9, p = .0001). Gains were maintained at long‐term follow‐up. Our results suggest that CBT is an effective treatment for child and adolescent OCD delivered in a clinical setting.