The purpose of the present study was to describe the computed tomography (CT) appearances of transient hepatic attenuation differences (THADs) in patients with acute pancreatitis and to discuss the mechanism of THAD. Two-phase dynamic CT images of 28 patients with acute pancreatitis were reviewed. Among them, THAD was seen in nine patients. All patients underwent ultrasonography, and four patients with THAD underwent surgery. Three types of THAD (THAD adjacent to the gallbladder in five of 28 patients, THAD with left lobar distribution in three of 28, wedge-shaped THAD in one of 28) were seen on the two-phase dynamic CT scans of patients with acute pancreatitis. In five patients, THAD disappeared when acute pancreatitis had subsided. THAD in acute pancreatitis is probably caused by increased arterial blood flow attributable to the inflamed lobe of the liver or the inflamed gallbladder. THAD in acute pancreatitis should not be confused with primary liver abnormalities.