Objective To observe the value of shear wave viscoelastography(SWV)for differentiating lung peripheral inflammatory masses and malignant tumors.Methods Conventional gray-scale ultrasound and SWV were prospectively performed in 70 patients with lung peripheral inflammatory mass or malignant tumor.The patients were divided into malignant group(n=42)and inflammatory group(n=28)according to pathological results.Clinical and ultrasonic data,including the maximum diameter of lesions,the mean Young's modulus(Emean),mean viscosity(Vmean),and mean dispersion slope(Dmean)were compared between groups.Receiver operating characteristic curves of ultrasonic parameters being significantly different between groups were drawn,and area under the curves(AUCs)were calculated to evaluate the efficacy of each parameter for differentiating lung peripheral inflammatory mass or malignant tumor.Results In malignant group,the maximum diameter and Emean of lesions were both higher,while Vmean and Dmean of lesions were both lower than those in inflammatory group(all P＜0.05).Vmean and Dmean of lesions had moderately/good efficacy for differentiating lung peripheral inflammatory mass or malignant tumor(AUC=0.843,0.866),both better than that of conventional ultrasound and Emean(AUC=0.673,0.685)(all P＜0.05).The combination of Emean,Vmean and Dmean had good efficacy for differentiating lung peripheral inflammatory masses and malignant tumors,with AUC of 0.874.Conclusion The viscous parameters of SWV could effectively differentiating lung peripheral inflammatory masses and malignant tumors.