Objective To investigate the value of contrast enhanced ultrasound (CEUS) imaging in the differential diagnosis between benign and malignant renal neoplasms.Methods Two hundred and fortyfive cases of renal space-occupying lesions confirmed by biopsy or surgical pathology were included in this study.The CEUS features of the renal space-occupying lesions,i.e.,the enhancement degree,homogeneity of enhancement,washing-in and washing-out time and enhancement pattern,were retrospectively analyzed.Results There were 210 cases of malignant renal tumors and 35 cases of benign lesions.The CEUS modes of the malignant renal tumors included "quick in and quick out" 82 cases,"quick in and slow out" 64 cases,"slow in and quick out" 18 cases and "slow in and slow out" 46 cases; good enhancement 150 cases (71.4％) and inhomogeneous enhancement 180 cases (85.7％).Both the contrast agent filling defect area and solid component enhancement of solid-cystic tumors were important features of malignant renal tumors.In the 35 cases of benign lesions,the CEUS modes included "quick in and quick out" 4 cases,"quick in and slow out" 8 cases,"slow in and quick out" 10 cases and "slow in and slow out" 13 cases.Most of the benign tumors showed low enhancement 51.4％ (18/35) and inhomogeneous enhancement 54.3％ (19/35).There were significant differences between the malignant and benign renal neoplasms in CEUS mode,degree of enhancement and homogeneity of enhancement (P ＜ 0.05),and in time of increasing,peak time,peak intensity and peak intensity ratio (P ＜ 0.05).The accuracy rates of contrast-enhanced ultrasound for diagnosis of benign and malignant tumors were 77.1％ and 83.8％,respectively,while the two-dimensional ultrasound diagnosis of benign and malignant tumors were 68.6％ and 76.7％,respectively,with a significant difference (P ＜ 0.05).Conclusions CEUS may provide more information to improve the diagnostic accuracy for renal neoplasms,and may play important role in differential diagnosis between benign and malignant renal lesions.