Study Design: Retrospective review of 31 consecutive female patients with adolescent idiopathic scoliosis undergoing selective thoracic fusion.Objective: To compare safety and efficacy of two techniques in treating adolescent idiopathic scoliosis undergoing selective thoracic fusion.Summary Of Background Data: There is paucity in the literature comparing posterior versus thoracoscopic instrumented fusion in scoliosis.Methods: Nineteen patients (group 1) underwent posterior instrumented fusion. Twelve patients (group 2) had thoracoscopic anterior instrumented fusion. All patients had a minimum of 25 months of follow-up observation.Results: Both groups were similar in terms of age at menarche and surgery. Preoperative Cobb angles in the coronal (erect and bending) and sagittal planes did not differ between the two groups. Group 1 patients had higher estimated blood loss (P = 0.006). Operative time (P < 0.001) and intensive care unit stay (P = 0.01) were longer in group 2 patients. There was no difference in parenteral analgesia requirement. There were no complications in group 1. Complications in group 2 included lobar collapse (1) and scapula winging (1). Improvement in scoliosis among group 1 patients averaged 77 (1 week), 72 (6 months), and 67% (most recent follow-up review). In group 2 patients, mean improvement in scoliosis was 66 (1 week), 62 (6 months), and 62% (most recent follow-up review). The differences between the two groups in terms of scoliosis improvement were not significant. Thoracic kyphosis (T2-T12) did not increase significantly with thoracoscopic versus posterior instrumentation. No significant change in lumbar lordosis (T12-S1) was noted with either procedure.Conclusions: The efficacy of thoracoscopic surgery was similar to standard posterior procedures. Advantages included lower intraoperative blood loss. The longer operative time and intensive care unit stay were attributed to the steep learning curve of this technique.