This study defines the normal anatomical relationships among the coracoacromial ligament, the deltoid, and the acromion in cadavers. The effect of arthroscopic acromioplasty on the acromial attachments of the coracoacromial ligament and the anterior fibers of the deltoid was also studied. After arthroscopic acromioplasty, the fibers of coracoacromial ligament and overlying deltoid inserting into the anterior part of the acromion remained attached to the acromion by a bridge of tissue composed of periosteum and collagen fibers of the coracoacromial ligament and deltoid tendon. We have called this the coracoacromial-deltoid-periosteal complex; it has not previously been described. This study demonstrates that arthroscopic acromioplasty preserves the acromial attachment of the coracoacromial ligament and the anterior fibers of the deltoid.