Abstract Background: Adolescence is a sensitive period of personal and psychological maturity, so many factors like a deformity and physical discomfort can affect the quality of life of patients with AIS. Disability and impaired quality of life are common in people with thoracic scoliosis. For society, work disability results in decreased productivity. The presence of a spinal deformity is a risk factor for psychological depression regard-less of the treatment the patient received. Aim of Study: The purpose of this study was to determine the effect of severity of Cobb angle of thoracic scoliosis in adolescence on the active range of motion of shoulder complex and cervical articulations in people with idiopathic scoliosis. Material and Methods: The study was conducted on 60 male and female patients and a control group consisting of 60 participants. Their age ranges from 12-18 years. The sample was sub grouped into three groups according to the severity of scoliosis and control group. Group 1 "G1": Twenty partic-ipants with Cobb angle 10-20 degree. Group 2 "G2": Twenty participants with Cobb angle 20-40 degree. Group 3 "G3": twenty participants with Cobb angle >40 degree. Group 4 "G4": Sixty participants with cobb angle 0 (control group). The ROM of cervical side bending, shoulder flexion and shoulder abduction on the convex side was recorded by digital camera and then was analyzed by kinovea software program. Results: There was a significant negative correlation between cobb angle and cervical side bending ROM, shoulder flexion and abduction ROM. However, this negative correlation increases with degree of severity of cobb angle. Conclusion: Based on the findings of this study, the severity of scoliosis affect the range of motion of shoulder joint and cervical spine.