This study was designed to examine the effect of incentive spirometry in pulmonary rehabilitation of children with cerebral palsy. The incentive spirometer, a device that can help improve breathing and strengthen inspiratory muscles. If the patient assigned to training group, the subjects started to respiratory muscle strengthening exercise using incentive spirometry. The training was performed ten sessions daily, for 4 weeks. Respiratory function tests including forced vital capacity, forced expiratory volume in 1 second, Peak cough flow, maximal phonation time were compared before interventions and at the end of exercise.