Abstract Background: The principal of scoliosis on pulmonary functions believed to be mechanical. The anatomical changes due to scoliosis in the chest wall causing impaired movement and reduced compliance that is demonstrable on pulmonary function testing (PFT). Aim of Study: To find the correlation between rib hump and ventilatory function in adult patients with idiopathic scoliosis. Material and Methods: Forty female adult patients with right thoracic idiopathic scoliosis enrolled in this study; they recruited from orthopedic outpatient clinics of Al Kasr Al-Aini Hospitals, Cairo University. The patient was asked to do Adam forward bend test which bend forward to bring the spine parallel with the floor, with the arms dangling, palms together, and knees forward, while the examiner inspected from behind for any thoracic or lumbar prominence that would signify scoliosis. Rip hump would be measured by scoliometer, then the patient would be given a spirometry to measure the ventilatory function. Results: There was significant direct strong negative correlation between rotation and FVC, there was significant direct strong negative correlation between rotation and FEV 1 while there is a non-significant negative weak correlation between rotation and FEV 1/FVC ratio. Conclusion: The degree of rotation of rib hump on patients with thoracic scoliosis correlate negatively with FVC, FEV 1 and no correlation between the rotation of the rib hump and the ratio between FEV1¤  FVC.