Objective To investigate the differences in tumor volume and metastatic tumors of the liver and regional lymph nodes between contrast-enhanced computed tomography (CT) and diffusion-weighted magnetic resonance imaging (DWMRI) through a comparative analysis,as well the useful information for target volume delineation,and to guide radiotherapy in clinical practice.Methods A total of 40 patients with pancreatic cancer were enrolled and underwent contrast-enhanced CT and DWMRI in the same position.The target volume was delineated,the major axis of the maximum tumor section was measured,and the numbers of liver metastatic tumors and metastatic tumors of the lymph nodes with a diameter of 5-8 mm or＞8 mm were measured based on the CT and DWMRI images.The analysis was performed by using paired t-test or paired Wilcoxon rank sum test.Results The mean gross tumor volume (GTV) delineated by contrast-enhanced CT and DWMRI was 54.95 cm3 and 41.67 cm3(P =0.000),and the mean value-different value was 13.28 cm3.The major axis of the maximum tumor section measured by contrast-enhanced CT and DWMRI were 4.18 cm and 3.94 cm (P=0.000),respectively,and in two patients,dCT was smaller than dDWMRI.A total of 83 liver metastatic tumors were identified by contrast-enhanced CT,and 112 were identified by DWMRI;the liver metastatic tumors detected by contrast-enhanced CT accounted for 74％ of those detected by DWMRI.As for the metastatic tumors of the lymph nodes with a diameter of 5-8 mm or＞8 mm,103 or 46 were detected by contrast-enhanced CT,and 200 or 56 were detected by DWMRI,and the tumors detected contrast-enhanced CT accounted for 52％ or 82％ of those detected by DWMRI.There were significant differences in all data between contrast-enhanced CT and DWMRI.Conclusions GTV and the major axis of the maximum tumor section measured by DWMRI are lower than those measured by contrast-enhanced CT,and contrast-enhanced CT is sensitive in detecting the metastatic tumors of the liver and lymph nodes.However,it is necessary to conduct further controlled experiments with reference to pathology.