Two cases of abnormal maxillary sinus were reported.
In one case, maxillary sinus was completely divided into two cavities by bony wall, and its parasinus had no communication with nasal cavity. Histologically, there were some different findings between mucous membranes of two cavities.
In another case, bony ridge in maxillary sinus was observed radiographically and when operated, it was proved that maxillary sinus was divided into two cavities by bony ridge incompletly.