All children are at risk for the development of an obstructive sleep apnea syndrome (OSAS) since adenotonsillar hypertrophy is widespread and the most common cause in children. The clinical picture, etiology and diagnostic approach of OSAS in children is discussed. Attention is given to the indications for polysomnography and the differences between adult and pediatric OSAS. An overview is presented of the different treatment modalities and the possible link between sudden infant death syndrome, pediatric OSAS and adult OSAS.