Procalcitonin is a diagnostic marker useful to discern infections and non-infectious complications in heart surgeries. The aim is to describe risk factors related to nosocomial pneumonia and the predictive value of serum procalcitonin in pediatric patients undergoing heart surgery. During a year a nested case-control study was carried out in a third level hospital. All patients undergoing open-heart surgery were followed and clinical data searching for pneumonia were registered every day. Blood samples for determination of procalcitonin were taken 48 hours after surgery. Those patients who developed pneumonia based on CDC clinical criteria were defined as cases; and controls were those patients who did not developed pneumonia. 188 patients underwent heart surgery (15 % developed pneumonia). Ninety-seven patients were submitted to open-heart surgery: 24 cases and 73 controls. Seventy-eight % of cases developed pneumonia between second and fifth day after surgery. The average time of surgery, extracorporial bypass, aortic cross-clamp, and mechanical ventilation were greater in control patients. The frequency of open sternotomy, reintubation, and surgical wound infections was greater in case patients. Some of the events related to heart surgery and their subsequent management are associated significantly to the development of hospital-acquired pneumonia.