Ectopic eruption of the maxillary canine tooth into surrounding tissue is familiar to us by many clinical cases from previous reports. Recently a 21-year- old female patient visited our department because of the symptoms and signs of chronic maxillary sinusitis for several years. Her paranasal X-ray showed severe inflammatory changes of both maxillary antrum and hard density which was presumed as impacted maxillary canine tooth of left side. During the Caldwell-Luc's operation it was confirmed that the canine tooth impacted in the left maxillary antrum.