Endoscopic removal of a maxillary dentigerous cyst. Developmental odontogenic cysts account for 10% of all cysts of the jaw. Dentigerous cysts are benign odontogenic cysts. They are associated with the crowns of unerupted teeth. A 24-year-old woman presented with headache, facial pain and facial swelling during the previous six months. Computed tomography revealed a dentigerous cyst in the right maxillary sinus floor. The cyst was removed and the tooth was extracted transnasally with the help of an endoscope. Our case was exceptional because it was seen in a rare area outside the dental area: it was located in the floor of the right maxillary sinus, and it was removed transnasally rather than with one of the more common approaches such as a Caldwell-Luc procedure. This article discusses the dentigerous cyst case, as well as the relevant literature.