Lemmel syndrome is a rare and misdiagnosed cause of acute abdominal pain due to a juxtapapillary duodenal diverticulum causing mechanical obstruction of the common bile duct. Frequently, patients suffering from Lemmel syndrome have a history of recurrent access to the emergency room for acute abdominal pain referable to a biliopancreatic obstruction, in the absence of lithiasis nuclei or solid lesions at radiological examinations. Ultrasonography (US) may be helpful in evaluation of upstream dilatation of extra-/intra-hepatic biliary duct, but computed tomography (CT) is the reference imaging modality for the diagnosis of periampullary duodenal diverticula compressing the intrapancreatic portion of the common bile duct. Recognition of this entity is crucial for targeted, timely therapy avoiding mismanagement and therapeutic delay. The aim of this paper is to report CT imaging findings and our experience in two patients affected by Lemmel syndrome.