Abstract: Objective To evaluate the value of 18 fluorodeoxyglucose（FDG） positron emission tomography and computed tomography（PET/CT） for restaging metastasis of mediastinal lymph nodes in patients with non-small cell lung cancer（NSCLC） after treatment. Methods Of the 51 NSCLC patients（41 men and 10 women） at a mean age of 61 years（range 34-90 years） included in this study,29 had squamous carcinoma,20 had adenocarcinoma,and 2 had adenosquamous carcinoma.If the SUV threshold cutoff was ＞3.5 according to prior receiver operating characteristic analysis,the lymph nodes were defined as positive. Results Mediastinal lymph nodes were detected in 45 of the 51 patients.The SUV value was ＞3.5 in 63%（79/125） lymph nodes,in 35%（28/79） lymph nodes less than 1cm in diameter,and in 65%（51/79） lymph nodes greater than 1cm in diameter,respectively.The positive rate of lymph nodes was 58%（46/79）,41%（32/79）,and 1%（1/79）in 20 patients with lung adenocarcinoma,in 29 patients with squamous carcinoma,and in 2 patients with adenosquamous carcinoma,respectively.No difference was found in the number of lymph nodes less or greater than 1cm in diameter between patients with lung adenocarcinoma and those with squamous carcinoma（χ²=18.25,P＜0.05）. Conclusion ¹⁸F-FDG PET/CT has a high predictive value for restaging metastasis of mediastinal lymph nodes in NSCL patients.