Obstructive sleep apnea (OSA) is a common disease in children. It is defined by the onset of snoring, hypopneas or apneas with impaired sleep and daytime function. Obstruction of the upper airway during sleep is the underlying pathogenetic mechanism. It is caused either by an anatomic obstruction, increased airway collapsibility or both. Normally OSA in children is diagnosed by its typical anamnesis including snoring and exerted breathing patterns. The diagnosis is confirmed in unclear cases using polysomnography. Treatment consists of conservative measures such as weight reduction and--provided appropriate anatomical findings exist--adenotonsillectomy or adenotonsillotomy. Surgery is an effective treatment for OSA in children as proven by numerous studies of high evidence levels.