The author have recently experienced and is reporting a clinical case of the dentigerous (follicular) cyst which was found in the anterior bony wall of the left maxillary sinus and accompained by the homolateral paranasal sinusitis. The patient was 21 year old, male student, and otherwise healthy. The case was treated succesfully with operative procedure, and the supernumerary tooth which resembled permanent canine morphologically was removed. The postoperative course was also uneventful.