A patient with obstructive jaundice was examined by multidetector row helical computed tomography (MDCT) and magnetic resonance imaging (MRI), and his common bile duct was observed to be leading into the distal portion of the horizontal duodenum with a pancreaticobiliary union outside the duodenal wall. A mass was also found in the proximal jejunum. All the above findings were confirmed by subsequent surgery, thus contrast-enhanced MDCT and MRI with appropriate image post-processing could provide non-invasive and accurate information regarding anatomy and lesions of the pancreaticobiliary duct and duodenal union, which may improve the feasibility of surgery and reduce postoperative complications.