The assumption that subacromial space decreases in patients with thoracic hyperkyphosis arises from sporadic and personal observations. The purpose of this study was to compare width of subacromial space calculated on radiographs and CT scans of a high number of patients with thoracic hyperkyphosis that registered on exams of healthy volunteers. We measured the subacromial space, using Petersson’s method, on radiographs of 47 patients with idiopathic or acquired thoracic hyperkyphosis and of 175 healthy shoulder volunteers. Both groups were further distinguished considering gender and age. Females with hyperkyphosis were also divided in two subgroups: those with a kyphotic curve of less (24 patients) or more (19 patients) than 50°, respectively. Subacromial space of all patients and of 21 volunteers was also evaluated using CT. Acromio-humeral space was less wide in patients with hyperkyphosis with respect to coeval volunteers of the same gender; in females and in subjects older than 60. Subacromial width of females with hyperkyphosis whose curve was more than 50° was significantly narrower (p<0.05) than that measured on radiograms or CT scans of females with a less severe spinal deformity. Decrease of subacromial space may be attributed to less posterior tilting of the scapula and to dyskinesis of the scapular movement. Scapular malposition causes an anomalous orientation of the acromion that may contribute to subacromial impingement. Patients with thoracic hyperkyphosis greater than 50° had a subacromial space narrower than that measured in patients with a less severe kyphosis. This suggests that subacromial width is directly related to severity of thoracic kyphosis. Because hyperkyphosis of patients with osteoporotic vertebral fractures may worsen over the time, subacromial decompression could give only temporary shoulder pain relief.