Abstract： Objective:To investigate the value of liver reporting and data system version 2018 (LI-RADS v2018) in the differential diagnosis between hepatocellular carcinoma (HCC) and other primary hepatic malignancy (OM) less than 3 cm.Methods:The data of total 95 patients with primary liver cancer confirmed by pathology from September 2014 to September 2019 in Central Hospital of Lishui City and Suichang People′s Hospital of Lishui City were retrospectively analyzed. The length of all the lesions were less than 3 cm. The patients were distributed into HCC group (53 cases) and OM group (42 cases, consisting of 31 cases of massive intrahepatic cholangiocarcinoma and 11 cases of combined hepatocellular-cholangiocarcinoma) according to the pathological results. Then the lesions were classified based on the MRI features according to the LI-RADS v2018 guidelines. The χ 2test was used to compare the MRI characteristics between the two groups. The sensitivity and specificity of LI-RADS v2018 in the diagnosis of HCC and OM were calculated based on pathology. Results:There were statistically significant differences in arterial enhancement, clearance, pseudocapsule sign, steatosis, hemorrhage and filling enhancement between the HCC group and OM group ( P<0.05). In HCC group, the number of lesions classified as LR-M, LR-3, LR-4 and LR-5 were 7, 1, 11 and 34, respectively. Meanwhile in OM group, the number of lesions were 15, 1, 15 and 11, respectively. Taking LR-5 as the criterion to predict HCC, the sensitivity was 64.2% (34/53) and the specificity was 73.8% (31/42). Taking LR-4/5 as the criterion to predict HCC, the sensitivity was 84.9% (45/53) and the specificity was 38.1 % (16/42). Taking LR-M as the criterion to predict OM, the sensitivity was 35.7% (15/42) and the specificity was 86.8% (46/53). Conclusion:On the condition that the length of intrahepatic lesions are less than 3.0 cm, the specificities of LR-4/5 and LR-5 criteria in the diagnosis of HCC are relatively low, meanwhile the specificity of LR-M criterion in the diagnosis of OM is high.