Sleep-related breathing disorders in children are common. Nearly 10% of preschool-aged children snore, and 1% of 4- to 5-year-old children present with an obstructive sleep apnea syndrome (OSAS), mostly due to an adenotonsillar hyperplasia. OSAS in children differs markedly from adults concerning etiology, clinical symptoms, polysomnographic findings, and course of the disease. Therefore, results of adult sleep medicine cannot easily be applied to children. The disease may result in pulmonary or systemic hypertension, failure to thrive, and neurocognitive misbehavior. Up to now, there is no consensus concerning diagnosis and therapy. In this article, we summarize and discuss what is known so far about sleep-related breathing disorders in children, focussing on the OSAS as the most important diagnosis for the ENT specialist.