The calcifying cystic odontogenic tumor or Gorlin cyst is an uncommon lesion with a variable clinical behavior and considerable histopathologic diversity. The authors report a case of calcifying cystic odontogenic tumor that was being treated as a maxillary sinus mucocele. The possibility of mimicking numerous odontogenic and nonodontogenic lesions makes the calcifying cystic odontogenic tumor difficult for a clinical diagnosis. The present case demonstrates that a specific knowledge in oral pathology is required to differentiate odontogenic lesions.