Background: The effectiveness of bracing on preventing curve progression in coronal plane for mild and moderate adolescent idiopathic scoliosis (AIS) patients has been confirmed by previous radiographic researches.However, a hypokyphotic effect on the sagittal plane has been reported by a few studies.A relatively increasing number of AIS patients were noticed to wear a new kind of elastic orthotic belt for the treatments of scoliosis without doctors instructions.We postulate the correcting mechanism of this new appliance may cause flattening of the spine.To our knowledge, no study has investigated the effects of this new orthosis on the sagittal profile of AIS patients.The aim of this study was to evaluate and compare the effects of elastic orthotic belt and Milwaukee brace on the sagittal alignment in AIS patients.Methods: Twenty-eight female AIS patients with mild or moderate thoracic curves were included in this study.Standing full-length lateral radiographs were obtained in three conditions: natural standing posture without any treatment, with elastic orthotic belt and with Milwaukee brace.Thoracic kyphosis (TK), lumber lordosis (LL) and pelvic incidence (PI) were measured and compared between the above three conditions.Results: Both elastic orthotic belt and Milwaukee brace can lead to significant decrease of TK, however, the decrease of TK after wearing elastic orthotic belt is significantly larger than that after wearing Milwaukee brace.Compared with no treatment, LL was found to be significantly smaller after wearing Milwaukee brace, however, such significant decrease was not noted after wearing elastic orthotic belt.No significant changes were observed for the PI between 3 conditions.Conclusions: The elastic orthotic belt could lead to more severe thoracic hypokyphosis when compared with Milwaukee brace.This belt may not be a suitable conservative method for the treatment of mild and moderate AIS patients.