Background: The long-term pulmonary function of patients with adolescent idiopathic scoliosis undergoing surgical correction is uncertain. To our knowledge, no report has demonstrated the changes in pulmonary function five years or more following spinal arthrodesis with use of modern segmental spinal instrumentation techniques for the treatment of all types of adolescent idiopathic scoliosis in a similar adolescent population. Methods: One hundred and eighteen patients with adolescent idiopathic scoliosis undergoing surgical treatment at a single institution were evaluated with pulmonary function tests to assess the absolute and percent-predicted value of forced vital capacity and forced expiratory volume in one second at the preoperative examination and at regular intervals postoperatively. The patients were divided into four groups depending upon the surgical procedure: Group 1 comprised forty-nine patients who had posterior spinal arthrodesis with iliac crest bone graft; Group 2, forty-one patients who had posterior spinal arthrodesis with thoracoplasty; Group 3, sixteen patients who had open anterior spinal arthrodesis with a rib resection thoracotomy; and Group 4, twelve patients who had combined anterior and posterior spinal arthrodesis with a rib resection thoracotomy and iliac crest bone graft, respectively. Results: A comparison of absolute pulmonary function values from the preoperative and final follow-up evaluations demonstrated a significant (p < 0.0001) increase in both the forced vital capacity and the forced expiratory volume in one second for Group 1, whereas no change was seen in those values for Groups 2, 3, and 4. A comparison of the changes in the percent-predicted pulmonary function values demonstrated significant (p < 0.05) decreases in forced vital capacity and forced expiratory volume in one second for Groups 2, 3, and 4, except for the latter value for Group 4, whereas Group 1 had no change. Conclusions: Patients who have had any type of chest cage disruption during the surgical treatment of adolescent idiopathic scoliosis demonstrate no change in the absolute value and a significant decline in the percent-predicted value of pulmonary functions at five years following surgery. Chest cage preservation is recommended to maximize both absolute and percent-predicted pulmonary function values after surgical treatment of adolescent idiopathic scoliosis. Level of Evidence: Therapeutic Level III.