Obstructive sleep-disordered breathing in children is a spectrum of disorders of breathing during sleep characterized by snoring and upper airway obstruction. In its most severe form, obstructive sleep apnea, prolonged complete upper airway obstruction occurs, disrupting normal ventilation and sleep patterns. The hallmark feature of the disorder is habitual and loud snoring. Adenotonsillar hypertrophy is the most common cause of obstructive sleep-disordered breathing. Left untreated, obstructive sleep-disordered breathing may lead to problems related to sleep disruption such as inattention, poor learning, behavioral problems, and attention deficit/hyperactivity disorder or may cause more serious morbidity, including growth failure and pulmonary hypertension. The diagnosis of obstructive sleep-disordered breathing in most children is made through a thorough sleep-based history and physical examination. Adenotonsillectomy, the cardinal treatment for obstructive sleep-disordered breathing, is curative in a large proportion of patients and markedly improves quality of life for children with the disorder.