Abstract: Objective To investigate the role of apparent diffusion coefficient （ADC） value in evaluating the therapeutic effect of transcatheter arterial chemoembolization （TACE） on large hepatocellular carcinoma with the minimum distance to the liver capsule≤1 cm. Methods The imaging data of 40 liver cancer patients with the minimum distance of the tumor to the liver capsule≤1 cm were retrospectively analyzed from January 2014 to July 2019 in Xiamen Chang Gung Hospital,Linkou Chang Gung Memorial Hospitaland Fukuang General Hospital of Liaoning Health Industry Group.All the patients underwent transcatheter arterial chemoembolization （TACE） twice.MRI plain scan and enhancement examination were performed 1 week before and after each TACE （with the interval of 1-3 months）.ADC values of 15 regions of interest （ROI） were measured on MRI （b=800 s/mm²）.Using DSA as the gold standard,the location,enhancement,lipiodol distribution and normal liver parenchyma around TACE were evaluated.The receiver operating characteristic curve （ROC） was drawn,and the cut-off value of ADC was identified,and its sensitivity and specificity were estimated. Results A total of 40 lesions were detected in 40 patients,and 541 ROIs were analyzed.A total of 95 active lesions （residual or recurrent tumor） were detected in the second DSA,and the corresponding ADC value was （0.94±0.37）×10^-3 mm²/s,while the ADC value of 446 inactive lesions（no residual or recurrent tumor） was （1.60±0.38）×10^-3 mm²/s.ROC curve analysis showed that the sensitivity and specificity of ADC was 86.8% and 87.4%,with cut-off value of 1.14×10^-3 mm²/s,and the AUC was 0.934.There was no significant difference in the ADC value of ROI3 （the area of the lesion adjacent to glisson's capsule） before and after operation （P=0.052）.The difference of ADC values of the ROIs in remaining lesions were significantly different before and after surgery （P<0.05）.There was no significant difference in ADC values of the ROIs in peripheral hepatic parenchyma before and after operation （P>0.05）. Conclusion ADC value can quantitatively evaluate the residule tumors of large hepatocellular carcinoma after TACE.