AIM: To investigate the specific value of resistance index (RI) in color Doppler ultrasonography in the diagnosis of focal hepatic lesions.METHODS: Eight hundred patients with 893 hepatic solid lesions were studied with color Doppler flow imaging (CDFI) and pulsed Doppler, induding 644 malignant cases (596 primary malignant liver tumors, and 48 metastatic liver tumors), 156 benign cases. All were confirmed by operation and pathology. RESULTS: The detection rate of arterial flow in malignant tumors was 92%, and 52% in benign lesions. Doppler spectrum analysis showed that the resistance index in primary malignant tumors was 0.75±0.12, 0.73±0.09 in metastatic tumors, and was below 0.6 in benign lesions.The difference was significant (P＜0.001). This difference was related with its histopathologic structure.CONCLUSION: The arterial flow with RI≥0.6 identified by CDFI within the liver lesion can be regarded as a criterion of malignant tumors, RI＜0.6 can be regarded as benign disorders.RI is useful in differential diagnosis of liver neoplasms.