Objective To explore the values of whole body diffusion-weighted MRI (WB-DWI) and WB-DWI in combination with conventional CT/MRI in diagnosis of metastases of malignant tumors. Materials and Methods 76 patients with malignant tumors underwent WB-DWI examinations. Patients with malignant tumors underwent conventional CT and MRI examinations within a week, few of which underwent enhanced CT OR MRI scan. Two experienced imaging physicians analyzed all of WBDWI, CT and MR images by double-blind method. All metastases were confirmed by surgery or puncture pathology, imaging data and laboratory tests or follow-up at least 3 months. The sensitivity, specificity and accuracy in the diagnosis of metastases of WBDWI and WB-DWI in combination with conventional CT/MRI were compared. Results The sensitivity, specificity and accuracy in detecting systemic metastases from malignant tumors were 75.9%, 25%, 69.8% respectively by WB-DWI, and 94.8%, 67.5%, 91.5% respectively by WB-DWI in combination with conventional CT/MRI. By the chi-square test, there were statistical differences in detecting systemic metastases from malignant tumors between the two methods (P>0.05). Conclusion WB-DWI in combination with conventional CT/MRI is a reasonable and effective screening tool in detecting systemic metastases from malignant tumors, with high clinical value.