Several diseases such as mucocele, postoperative maxillary cyst, radicular cyst and odontogenic keratocyst could be shown as cystic lesion in the maxillary sinus on computed tomography. The aim of this study is to evaluate clinical and radiological points in the differential diagnosis of maxillary cystic lesions. Twenty-eight cases of these lesions on computed on tomograms were classified into twenty-two postoperative maxillary cysts, three maxillary mucoceles, two odontogenic keratocysts and one radicular cyst. The results showed clinical and radiological findings could suggest the final diagnosis of cystic lesions in maxillary sinuses.