Anorexia and Bulimia nervosa are common psychiatric disorders in adolescent girls. In discrepancy to ICD-10 and DSM-IV we would propose the 10th BMI percentile as weight criterium for anorexia nervosa. Both disorders have a high somatic and psychiatric comorbidity; the most severe complication at long term follow-up is osteoporosis. The most prevalent psychiatric disorders are affective disorders, anxiety and obsessive-compulsive disorder and substance abuse. There is undoubtedly a genetic predisposition and a range of general and personal environmental risk factors. Treatment of adolescent eating disorders mostly requires a multimodal approach which consists of several components, e.g. weight rehabilitation, nutritional counselling, individual and family psychotherapy, and treatment of comorbid psychiatric disorders.