We have recently experienced a case of calcifying epithelial odontogenic tumor in the right maxillary sinus. This calcifying epithelial odontogenic tumor made patient suffering from right nasal obstruction and right cheek swelling for 10 months. X-ray of PNS revealed hazy density with a teeth shadow and destructed bony wall of right maxillary sinus. Orbital floor was not destructed. We have performed right Denker's operation and removed a mass of 6.5×3.5×2cm in size which had a molar teeth. Pathological diagnosis was ""calcifying epithelial odontogenic tumor involving right maxillary sinus"", which was a very rare tumor. The postoperative course was unevenful.