Adolescent idiopathic scoliosis (AIS) is a three-dimensional structural deformity of the spine, the etiology of which is not clearly known, and can be seen from the age of 10 until the skeletal system matures. The Scoliosis Research Society (SRS) defines AIS as vertebral rotation and a Cobb angle of 10° or greater. Its incidence varies between 0.47% and 5.2%. It is more common in women than in men. In patients with a Cobb angle greater than 40° or who are not yet bone-mature and who are continuously progressing, surgical intervention is often performed with posterior spinal fusion. Scoliosis negatively affects not only the appearance of patients but also their lung functions through differentiation in thoracic morphology and progression of spinal curvature. The severity of this restrictive pattern in lung functions can be assessed with pulmonary function tests (PFT). However, this test requires patient cooperation and is particularly difficult to perform in patients with cognitive dysfunction. Despite studies recommending the use of pulmonary function tests in preoperative risk assessment, the literature shows inconsistency in predicting the need for postoperative intubation and mechanical ventilation. In this study, the effect of preoperative pulmonary function tests (PFT) performed before AIS surgery on the need for intensive care admission will be evaluated. In addition, the potential relationships between PFT results and intraoperative and postoperative blood transfusion needs, postoperative intubation needs, hospital stay, mortality status, inotropic support needs, Cobb angle, scoliosis location, and the number of affected vertebrae will be investigated.