This report describes the presence of an unusually wide branch of the posterior superior alveolar artery, which descends from the maxillary sinus through the maxillary alveolar bone to the palatal aspect of the alveolar crest. While this intrabony structure was clearly demonstrated using a reformatting program of computed tomography (CT), it was difficult to definitely identify by panoramic or periapical radiographs. Complications in implant treatment were thus avoided by preoperative analysis of the tomography. Keywords: anatomic variation, computed tomography, dental implants