ABSTRACT Cerebral palsy is a non-progressive brain lesion that causes many disabilities in children. Spastic diplegia is a subtype of spastic cerebral palsy in which the legs are the most affected limbs. They experience significant sitting, standing, and walking problems because of spasticity, excessive muscle weakness, kinematic joint abnormalities, and reduced postural control. It affects primarily motor dysfunction and causes secondary musculoskeletal problems and respiratory dysfunction from weakness of respiratory muscles, which have a common function in respiration and trunk control that by strengthening them may affect positively on both respiration and trunk control. Children with CP have insufficient ability to control postures compared to normal children because of abnormal muscle coordination patterns in the sitting position. Leads to the loss of trunk balance and resultant increases in the muscle tone of the upper and lower limbs. Respiratory muscles play a dual role in breathing and trunk balance during exercise. CP patients have impaired respiratory function because of muscular weakness and postural trunk dysfunction. One of rehabilitations tools is the incentive spirometer exercise that has beneficial for children with cerebral palsy as it is inexpensive, simple and safe for children to use. Application of incentive spirometer as a training device for respiratory muscle help in improving strength of those muscles playing a great role improving both respiration and trunk control as a part of position stability as diaphragm and abdominal muscles have role in function of both respiration and stability.