BACKGROUND—Pulmonary function in patients with adolescent idiopathic scoliosis many years after posterior spinal surgery or brace treatment has not been documented. METHODS—A consecutive group of patients treated by posterior fusion or a brace at least 20 years previously was investigated. 90% attended a clinical follow up. Lung volumes were determined before treatment in 251 patients, 1.4 years after surgery in 141 patients, and 25 years after surgery or start of brace treatment in 110patients. Vital capacity (VC) was calculated as percentage predicted according to height and age and the results were corrected for loss of height due to scoliosis. Scoliosis angles were measured and smoking habits were recorded. An age and sex matched control group was also examined with the same questionnaire and pulmonary function tests. RESULTS—VC increased from 67% predicted immediately before surgery to 73% (p