Postoperative diaphragm paralysis after pediatric heart surgery is the cause of respiratory insufficiency for which there is currently no agreed treatment. The two hypotheses now considered are: early folding of the diaphragm or longterm assisted ventilation. A retrospective study from 1988 to January 1995 on the incidence of diaphragm paralysis and the type of treatment performed was carried out by the Department of Pediatric Heart Surgery of the Bambino Gesù Hospital in Rome. A total of 25 patients presented diaphragm paralysis out of 3400 operations performed and the clinical records of these patients in intensive care were reexamined. The patients were aged between 2 days and 5 years (mean 3 years) and weighed between 3 kg and 15 kg (mean 6.5). The diagnosis of diaphragm paralysis was made using fluoroscopy of the pulmonary fields during spontaneous breathing; 13 patients were extubated 7 days after diagnosis, 12 underwent surgical folding and were extubated immediately after surgery. The authors underline the particular intolerance to ventilatory insufficiency of pediatric patients after the correction of congenital cardiopathies and the need for early intervention to shorten the stay in intensive care and to avoid the onset of other severe complications such as infection. In particular, in patients undergoing Glenn's or Fontan's modified operation, the integrity of the ventilatory apparatus is essential for the correct function of the new hemodynamic status.