Abstract: Objective To explore the predictive value of diffusion weighted magnetic resonance imaging (DWI) and apparent diffusion coefficients (ADC) in chemotherapy for patients with metastatic tumor of liver.Methods Eighty patients (with 148 lesions) with gastrointestinal hepatic metastases were enrolled.The maximum diameters of the metastases tumor were compared before and after the treatment,and patients were divided into sensitive group and ineffective group according to the tumor diameter.Correlation between the ADC value and the diameter was analyzed,and the ROC curve was drawn to predict the sensitivity and specificity of the therapy.Results The maximum diameter of the tumor was similar in the two groups,and the ADC value of the sensitive group was significantly less than the ineffective group before treatment (P =0.000).In the aspect of ADC,the ADC value increased significantly in the sensitive group after 2 weeks or 12 weeks of treatment.The ADC value before treatment had negative correlation with the change of the diameter of the tumor(r =-0.662,P =0.000),and the change of ADC value after two weeks of treatment had negative correlation with the change of the diameter of the tumor as well(r =-0.846,P =0.000).The AUC value for ADC before treatment was 0.914.The AUC value for the changing rate of ADC after two weeks of treatment was 0.893.In combination of the ADC value before and after two weeks of treatment,the AUC increased significantly.Conclusion The ADC value before treatment,the change of ADC value after two weeks of treatment and collaborative assessment has favorable effective functions for the forecast of the chemotherapy effect on patients with colorectal and gastric cancer.