To evaluate the diagnostic value of CT scan in maxillary sinus diseases, CT findings in 100 cases of maxillary sinus diseases, which included 64 inflammatory diseases; 14 benign tumors; 17 malignant tumors and 5 fractures The result showed that the accordance rate between CT scan and operative diagnosis was 95.0%; between CT scan and pathology was 92.6%(88/95). It is concluded that CT scan showed a better visualization of maxillary sinus than X-ray tomogram.