Purpose: To evaluate the efficacy of the arterial phase of dynamic spiral CT in the detection of pancreatic adenocarcinoma compared with the late phase. Materials and Methods: Two phase spiral CT images of seventeen patients with pathologically proven pancreatic ductal adenocarcinomas were compared retrospectively. CT scans were performed with 5 mm collimation at 1:1 pitch table speed. Images of arterial and late phases were obtained at 35 seconds and 180 seconds after initiation of administration of 100 mL of contrast material(3 mL/sec), respectively.Images of the arterial phase were compared with those of the late phase. Results: Images of the arterial phase showed sufficient contrast between the tumor and adjacent pancreatic parenchyma in 12 cases, insufficient in fourcases, and no significant contrast in one case. Images of the late phase showed sufficient contrast in five cases, insufficient in five cases, and no significant contrast in seven cases. Images of the arterial phase was superiorto that of the late phase in 12 patients(70.6%). In six of this 12 patients, only the images of the arterial phase showed contrast between the tumor and the adjacent parenchyma. The images of late phase showed only one case of three metastasis detected on the images of the arterial phase. Conclusion: The arterial phase of spiral CT issuperior to the late phase that is comparable with conventional CT in the detection of pancreatic adenocarcinoma.