Acute pancreatitis is an acute inflammation of the pancreas and potentially dangerous for life. The revised Atlanta classification describes two forms of acute pancreatitis: interstitial edematous pancreatitis (the most frequent, 90–95% of cases) and necrotizing pancreatitis (less frequent, about 5% of cases). The diagnosis of acute pancreatitis is usually based on clinical and laboratory criteria, however imaging and in particular computed tomography with contrast medium can be of fundamental importance in clarifying the diagnosis when clinical and laboratory findings are discordant, identifying the cause, detecting complications and establishing the prognosis by assessing severity. In this regard, computed tomography severity scores have been developed, the most famous of which is the computed tomography severity index which classifies pancreatitis taking into account Balthazar grades (degree of inflammation of the pancreas and presence of collections) and the extent of necrosis; these scoring systems are designed to guide the management of patients with acute pancreatitis.