Malignant tumor of the paranasal sinus is a rare, occurring most frequently in the maxillary sinus. Carcinomas of the maxillary sinus are usually diagnosed at the advanced stage because most tumors have no symptom or nonspecific symptoms such as pain, nasal obstruction, rhinorrhea, and epistaxis. In addition to these features, it is difficult to distinguish carcinoma from inflammatory or cystic lesion on imaging study until the carcinoma destroys the surrounding structures. Therefore, the diagnosis is prone to be delayed. Here, we report a case of an 83‐year‐old male with nonkeratinizing carcinoma on the maxillary sinus, which was initially misdiagnosed as a cystic lesion. The aim of this study is to emphasize the effort for early diagnosis in order to improve prognosis and avoid inadequate treatment