Plastic bronchitis is characterised by the formation of large bronchial casts, which develop in the tracheobronchial tree and can cause airway obstruction. It has been increasingly encountered in more recent years as a serious complication of the Fontan operation with a reported mortality of up to 50% [Am. J. Respir. Crit. Care Med. 155 (1997) 364]. We report a case of a 4-year-old girl with Fontan circulation who developed plastic bronchitis and was successfully treated.