Abstract： Objective To compare the 18F-FDG PET metabolic characteristics and VHRCT morphological characteristics between invasive and non-invasive adenocarcinoma presenting as pure ground-glass nodules(pGGN).Methods Fifty-one patients with pGGN from October 2010 to June 2016 were retrospectively enrolled in this study.There were totally 52 lesions with sizes of no more than 30 mm and were grouped depending on pathological and follow-up diagnosis (31 lesions in the invasive adenocarcinoma group and 21 lesions in the non-invasive group).Clinical and imaging features were analyzed including age,gender,lesion location,size,density,SUVmax T/N,spiculation,lobulation,pleural indentation,vascular connection signs,vacuole sign and the air bronchogram.T test or x2-test was used in the comparison of different manifestations between the two groups.Logistic regression analysis on clinical parameters was applied.The ROC curve was used to find the cutoff of T/N.Results In the invasive adenocarcinoma group,T/N,SUV density and size were 1.97±0.71,1.16±0.54,-(431±104)HU,(18.48±5.65)mm,respectively.In the non-invasive group,T/N,SUVmax density,size were 1.20±0.28,0.64±0.20,-(533± 109)HU,(12.05±5.04)mm,respectively.The differences of T/N,SUVmax density and size had statistical significance between the two groups (t=-5.40,-4.87,-3.39,-4.21,P＜0.05).Lobulation and vascular connection signs in the invasive adenocarcinoma group were found in 21 and 13 cases respectively,while in the non-invasive group,they were present in 2 and 1 case,respectively,which showed significant differences between the two groups(x2=17.85,7.01,P＜0.05).T/N,lobulation,and vascular connection signs were the independent factors for the differentiation of benign and malignant lesions.The ORs were 52.547,8.375,72.206,respectively.When T/N=l.62,the area under the ROC curve was 0.885.The sensitivity,specificity and accuracy were 77.42％,90.48％,82.69％,respectively.Conclusions Pulmonary pGGNwith T/N no less than 1.62,lobulation and vascular connection sign indicates an invasive adenocarcinoma.