The author have recently experienced three cases of the dentigerous cysts, and a case of inverse tooth in right nasal cavity. One of the cyst was located in the left hard palate, and the another two cases were in inferior wall of the left maxillary sinus. Caldwell-Luc’s operations were performed for two cases of dentigerous cysts of the maxillary sinus, and a supernumerary tooth, morphologically resembled permanent premolar was removed, and the another one, resembled permanent molar, hardly impacted into the alveolar bone, was not extracted. A supernumerary tooth, resembled permanent canine, was removed with the cyst from the left hard palate. A inverse tooth which resembled permanent canine was located in the junction of right nasal septum and anterior margin of nasal floor, was seen during routine physical examination, and was also removed easily under anterior rhinoscopy.