This study examined the hypothesis that ipsilateral upper extremity elevation for muscle-sparing thoracotomy procedures contributes to the postoperative shoulder pain. Prospective observational study. Medical center. ASA physical status 1-2 patients undergoing elective lung surgeries including pneumonectomy, lobectomy, and segmentectomy performed through either the anterolateral approach or video-assisted thoracotomy surgery. Postoperative observation of ipsilateral shoulder pain. Postoperative examinations of sites of shoulder pain (clavicle, anterior, lateral,or posterior aspect of acromion, posterior neck, supraspinatus, infraspinatus, and these entire areas) with or without trigger points, visual analog scale score of wound pain, and requested counts of analgesics. The number of patients who suffered from postoperative shoulder pain was 37 of 70 (52.9%). Demographic data, anterolateral/VATS ratio, VAS scores, and requested counts of rescue analgesics requirement were similar in the groups of patients with and without postoperative shoulder pain. The segmentectomy caused a significantly higher incidence of postoperative shoulder pain compared with other procedures (p < 0.05). The supra- and infraspinatus were significantly higher areas of painful regions compared to the other sites. The 16 of 37 patients (43.2%) with shoulder pain showed defined trigger points in their painful areas. These results supported the hypothesis that myofascial involvement contributed, to some extent, to shoulder pain after muscle-sparing thoracotomy with ipsilateral upper extremity elevation.