The purpose of this retrospective study was to determine the most appropriate distal fusion level in terms of clinical results and radiological changes in Lenke 3C adolescent idiopathic scoliosis (AIS). Between June 2010 and May 2014, a total of 90 consecutive patients who underwent surgery for Lenke 3C AIS were divided into three groups as L2, L3, and L4 according to the fusion levels and compared in terms of functional and radiological outcomes. Patients were evaluated with Scoliosis Research Society 22 (SRS 22) and the Oswestry disability index (ODI) at the final follow-up. Preoperative standard posteroanterior and lateral whole-spine radiographs and lateral bending radiographs were used to evaluate the curves. All patients were also assessed with lumbar MRI at the final follow-up, and classified for each patient in terms of disc degeneration (DD) and facet joint degeneration (FJD). There was a statistically significant difference between the groups in terms of ODI category (P = 0.001). The rate of minimal disability in the L3 group, moderate disability in the L2 group, and severe disability in the L4 group were higher. Statistically significant differences were observed between the groups in terms of pain, body image, mental health, and total score distribution from the SRS-22 domains (P < 0.05). No significant difference was observed between the groups in terms of DD and FJD in MRI (P = 0.263). Although the preoperative functional scores could not be evaluated due to the retrospective nature of the study, it was observed that the only significant difference between the groups was the SRS-22 score. The best SRS-22 score was obtained in patients in whom fusion was stopped at L3.