This article provides an overview of the state of knowledge on behavioral and psychiatric disorders in children and adolescents. It describes problems of defining and classifying psychiatric illness in childhood and adolescence as well as special characteristics of clinical manifestations, etiological concepts and empirical study results. Furthermore, the utilization of health care facilities as well as results of epidemiological studies on total prevalence rates in childhood and adolescence is outlined. Contrary to general assumptions, an increase or decrease of total prevalence rates over the last decades cannot be derived from national and international studies. Finally, basic approaches for improvement of psychosocial care facilities for affected children and adolescents are described.