Between 1984 and 2007, 20 patients, admitted to our hospital for the treatment of thoracic outlet syndrome (TOS), were analyzed. Of these 20 patients, 2 subsequently entered rehabilitation to strengthen the muscle power surrounding the shoulder, 5 were followed by a brachial plexus anesthesiological block for the purpose of both diagnosis and treatment of TOS, and the other 13 patients underwent a total of 18 surgeries. Surgical methods consisted of a supraclavicular first rib resection with anterior and middle scalenectomy (SCFR + AMS) in 16 surgeries, and a transaxillary first rib resection (TAFR) in 2 surgeries. Preoperative symptoms disappeared immediately after surgery in all cases except for 1 that was treated by a TAFR. The surgical result of SCFR + AMS was favorable and effective to prevent a symptomatic recurrence due to the postoperative re-adhesion. We measured the inclination of the clavicle in these TOS patients, using a chest X-ray, which determines indirectly the width of the costoclavicular space, and compared it with that of 18 patients with cervical diseases, including cervical spondylosis and cervical disc herniation, who were operated on at our institution. By comparison of the inclination angle of the clavicle between the injured and the non-injured side in each diseases, it was shown that the injured side had declined by 3.0 degrees but than the non-injured side in TOS, more by only -0.1 degrees in the cervical diseases. This method may be utilized as an assistant diagnosis to discriminate between TOS and cervical diseases.