The MRI appearance of the subacromial/subdeltoid (SA-SD) bursa is described here in both healthy and pathological conditions. Based on one case of rotator cuff tear and intrabursal fluid outlined by two adjacent fat stripes we reviewed 20 shoulder MR examinations to define the normal and abnormal appearance of the peribursal fat. We found four pathological patterns: lateral displacement, tear-drop configuration, obliteration and double fat stripe.