The traditional method of thoracoabdominal retroperitoneal approach requires dissection of diaphragm which bears potential complications such as postoperatively weakened abdominal breathing and dysfunction of diaphragm.Mini-open anterior instrumentation with diaphragm sparing is designed to minimize the damage to diaphragm and improve cosmesis.This study compared the traditional anterior instrumentation and mini-open anterior instrumentation under the hypothesis that both results in similar surgical outcomes in treating thoracolumbar scoliosis.In Group A, 38 patients with an average age of 16.5 years underwent mini-open anterior instrumentation with diaphragm sparing.The average standing coronal Cobb angle was 56.4° in Group A.Thirty-eight patients with average age of 16.7 years in Group B received traditional open approach.The preoperative average Cobb angle was 55.8° in Group B.The average correction rate of coronal curve was 78% in group A while 75% in group B.No statistical difference between the two groups in terms of coronal curve correction, sagittal profile restoration and estimated blood loss was observed.The operation time was significantly higher in Group A than that in Group B.All patients in the two groups had good healing of incisions without neurological and instrumental complications during minimal 2 year follow-up.In Groups A and B, two patients suffered from pleural effusion, respectively.The wedging of the vertebral discs distal to the lowest fused level occurred in three and four patients in Group A and B, respectively.One case in group B was found to be suspicious pseudoarthrosis without loss of correction.Mini-open anterior instrumentation with diaphragm sparing could minimize the surgical invasion as well as achieve similar clinical outcomes compared with classical anterior approach.