Fibrous dysplasia (FD) in the paranasal sinuses is uncommon, and its management may be difficult. We report the case of a 25-year-old female with FD exhibiting a cystic appearance in the maxillary sinus. The patient had been complaining of facial swelling for few years. Imagery study showed a cystic lesion and dense bone changes in the maxillary bone. Inferior meatal antrostomy with a nasal endoscope failed to confirm a histological diagnosis. After a 3-year follow-up, the degree of facial swelling was unchanged, and the patient underwent middle meatal antrostomy and was diagnosed with FD.