There is a controversy in results about influence of surgery on pulmonary function in idiopathic scoliosis. The aim of the study was to study pulmonary function in severe thoracic idiopathic scoliosis and to detect changes in pulmonary function after the three-dimensional anterior surgical correction in severe thoracic scoliosis. 91 patients at the age of 16 +/- 5.1 yrs underwent surgery in order to make a correction of scoliotic deformity. All the curves were greater than 70 degrees (86 +/- 5.1). Group I consisted of 60 patients with scoliotic curves between 70 degrees and 100 degrees, while group II consisted of 31 patients with curves greater than 100 degrees. All the patients were operated by anterior instrumentation and the average correction was 74% +/- 15 for group I, and 71% +/- 18 for group II. Vital capacity (VC) and forced expiratory volume in the first second (FEV1) in group I remained unchanged. In group II, VC improved for 11%, while forced expiratory volume (FEV) improved for 13.6%. Our conclusion is that there is a significant correlation between the percentage of achieved correction and pulmonary function.