Objective To evaluate the air bronchograpm in the differential diagnosis of peripheral solitary pulmonary nodule(3 cm or less) by computed tomography (CT). Methods The thin section CT images of air bronchogram in 190 eases with peripheral solitary pulmonary nodule confirmed by surgical resection and/or bronehoscopy and/or percutaneous needle biopsy and histopathology were analysed. Results The air bronchogram was seen in 52/100(52%) cases with peripheral lung cancers and in 29/50 cases (58%) with inflammatory pseudotumors on CT scans. Of lung cancers, there were adenocareinoma in 23/31 eases, squamous cell carcinoma in 14/41 cases, adenosquamous carcinom in 4/5 cases,small cell carcinoma in 7/14 cases and poorly differentiate carcinoma in 5/9 cases. The air bronchograms were not seen in 32 tuberculomas,5 hamartomas and 3 pulmonary cysts. Conclusion Air bronchogram can be seen in several pnlmonary nodules,it does not appear to be the characteristic of small peripheral carcinoma especially adenocarcinoma, and it alsc can not be helpful in distingushing malignant and benign pulmonary nodules.