© Wolters Kluwer Health, Inc. All rights reserved.Objective We aim to investigate a possible relationship between acute pancreatitis (AP) and body fat and muscle parameters in computed tomography (CT). Methods Computed tomography images of 107 patients with AP were scored in terms of AP severity using the modified CT severity index. Muscle mass, muscle mass index, visceral and subcutaneous adipose tissue area, multifidus muscle/fat attenuation ratio, total psoas index (TPI) and Hounsfield units average calculation (HUAC) values were performed. Results Total psoas index and HUAC of mild AP cases were significantly higher than those with moderate and severe AP. The TPI of patients with severe pancreatic necrosis were found to be significantly lower than those without necrosis. Hounsfield units average calculation of cases without necrosis were significantly higher than those with severe necrosis in the pancreas. Conclusions Our study indicated that lower volume and density of psoas muscle associated with worse CT severity score and larger pancreatic necrosis in patients with AP.