The clinical utility of diffusion-weighted magnetic resonance imaging (DWI) was originally established for acute stroke; however, recent studies suggest that DWI may be more sensitive and specific for the detection and staging of malignant tumors than either computed tomography (CT) or ultrasonography (US). We herein present 4 cases of pancreatic cancer that were detected by DWI and subsequently discuss the efficacy of DWI for the diagnosis pancreatic cancer. We performed both DWI and dynamic CT examinations on 4 patients with pancreatic cancer. MR examinations were performed with a 1.5-T imager (Toshiba). We measured the signal intensity in a series of DWI images and calculated the apparent diffusion coefficient (ADC) values to differentiate the tumors from normal tissue, inflammation, or another lesion. Two radiologists analyzed the DWI and CT images, and the evaluation of the primary tumor (T), regional lymph nodes (N), and distant metastatic disease (M) was conducted according to the TMN classification system. There were no differences between the DWI and the CT images regarding their abilities to detect advanced pancreatic cancer. However, DWI displayed superior ability in detecting early stage tumors and evaluating the degree of tumor invasion. DWI has the potential to be clinically effective in the detection of early pancreatic cancer, and DWI can be a powerful tool for the evaluation of pancreatic cancer.