Objective To explore the application of 18F-FDG PET/CT combined with high-resolution CT (HRCT) in the same scanner on diagnosis of lung cancer, and its influencing factors. Methods 50 patients, in which some cannot supply HRCT raw date and under highly suspicion of being lung cancer, some were postoperative lung cancer and metastasis of lung cancer, were examined by 18F-FDG PET/CT combined with HRCT in the same scanner. Results 50 patients were all successful (100%) on PET/CT scans after preparation, injection, rest and breathing exercises;46 cases (92%) were successful on PET/CT combined with HRCT scans;4 cases (8%) failed on HRCT scans. Ma-lignant lesions were found in 35 cases, with the metastasis of 21 cases;4 in 6 cases of postoperative lung cancer were found metastasis;9 cases of benign pulmonary nodules need to be observed sequentially. Conclusion 18F-FDG PET/CT combined with HRCT in the same scan-ner is valuable on diagnosis of lung cancer. The diagnostic accuracy and sensitivity significantly increase. It is a non-invasive new imaging technology and systemic metastasis can be observed.