Objective:To investigate the value of PET/CT with 18F-FDG in the diagnosis of lung cancer. Methods:A retrospective analysis was performed on 168 patients with pulmonary lesions (115 malignant,53 benign) by 18F-FDG PET/CT from October 2006 to January 2009. The shape was surveyed based on CT. The SUVmax in region of interest (ROI) of pulmonary lesion was calculated on PET. Imaging information was interpreted and compared with histopathology findings or other diagnostic procedures. Results:In 168 patients with pulmonary lesions,the sensitivity,specificity and accuracy of CT,PET and PET/CT in the diagnosis were as follows:73.9%(85/115),73.6%(39/53),73.8%(124/168) for CT alone; 82.6%(95/115),62.3%(33/53),76.2%(128/168)for PET alone;90.4%(104/115),81.1%(43/53),87.5%(147/168) for PET/CT scan. Among 55 patients with lung cancer undergone operation,there were 31 cases with and 24 without mediastinal and hilar nodal metastases. The sensitivity,specificity and accuracy of PET/CT in the diagnosis of mediastinal and hilar nodal metastases were 90.3%,95.8%,92.7%,respectively. Metastases were identified in 41 patients. 105 bone metastasis lesions were found by PET/CT,only 25 lesions showed lytic type on CT images. Conclusion:PET/CT is of greater value on the differential diagnosis of pulmonary than PET or CT alone. The sensitivity,specificity and accuracy of diagnosis are significantly improved by PET/CT scan,which may be useful in diagnosis and staging of lung cancer.