Respiratory disorders that occur in children asleep are frequent. They are evaluated by studying the respiratory function at each stage of sleep, as determined by neurophysiological criteria, and they must be interpreted on the basis of what is known of respiratory adaptation during sleep in healthy infants. Respiratory disorders during sleep may be due to: (1) obstructive sleep apnoea syndrome caused by an obstruction of the upper airways, most frequently by enlarged tonsils; (2) nocturnal episodes of acute on chronic obstructive lung disease, such as cystic fibrosis, sequelae of viral infection, ciliary dysfunction, broncho-pulmonary dysplasia; (3) nocturnal asthma; (4) alveolar hypoventilation of central origin. The short-or long-term risk of respiratory disorders during sleep is their repercussions on pulmonary circulation and right heart function.