Abstract: Objective To evaluate the diagnostic value of ¹⁸F-FDG positron emission tomography (PET) in mediastinal staging of lung cancer.Method A retrospective analysis of mediastial staging was carried out in 41 cases of lung cancer by comparing the preoperative mediastinal FDG PET and CT findings with the pathological results. Results According to the pathological results,18 patients had mediastinal matestasis,17 of whom were correctly identified by FDG PET,and 10 by CT. Of the other 23 patients without mediastinal mateatasis pathologically,22 were correctly diagnosed by FDG PET and 20 by CT. The sensitivity and accuracy for diagnosis of regional mediastinal lymph node matestasis with FDG PET were 94.4% and 95.1%,obviously higher than those of CT (55.6% and 73.2%,P<0.05).Conclusion FDG PET is a better alternative for mediastinal staging of lung cancer,specially for identification of small lymph node metastasis escaping detection by CT,to provide important evidence for clinical staging and treatment planning of lung cancer.