PURPOSE: To perform a study to investigate the influence of posterior scoliosis surgery and thoracoplasty on pulmonary function. METHODS: This was a retrospective observational study of 37 patients with AIS who underwent posterior instrumented surgical correction with thoracoplasty. There was a minimum of 2 years follow-up. Clinical outcomes were measured using the SRS-22 questionnaires. Radiological outcomes were evaluated using standing posteroanterior and lateral radiographs. All patients had pulmonary function tests to evaluate pulmonary volume and flow (forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC)) both before surgery and at the final follow-up. RESULTS: There were three males and 34 females. The mean age of patients was 14.6 years (range 11-21 years). The mean length of follow was 58 months (range 24-124 months). The average main thoracic Cobb angle in the coronal plane was corrected from 50.0° ± 12.4° preoperatively to 16.6° ± 6.3° postoperatively. The average thoracolumbar Cobb angle in the coronal plane was corrected from 28.2° ± 10.6° preoperatively to 10.1° ± 7.2°. The average thoracic kyphosis angle was corrected from 17.4° ± 11.0° preoperatively to 21.8° ± 10.5°. In terms of the Quality of life Outcomes (QoL), there was a significant increase (p < 0.001) in the mean SRS 22 scores from 3.8 preoperatively to 4.3 postoperatively. A statistically significant increase in the absolute forced expiratory volume in one second (FEV1) from pre-operative values with a p value < 0.001 was seen. There was a statistically significant increase in percentage predicted forced expiratory volume in one second from preoperative values with a p value of 0.008. There was also a statistically significant increase in the absolute forced vital capacity (FVC) from preoperative values with a p value < 0.001. The average percentage predicted forced vital capacity did increase on final follow-up from before surgery, but the increase was not statistically significant. CONCLUSIONS: We have demonstrated that pulmonary function post-thoracoplasty not only reaches pre-operative levels, but significantly surpasses it with regards to the majority of the pulmonary parameters measured in this study. We also demonstrated satisfactory radiological correction and clinical outcomes.