Computed tomography is mandatory in the investigation of the acute abdomen and can provide the physician with crucial information to decide whether the patient should be treated surgically or conservatively. An unusual cause of acute abdomen is presented. Computed tomography suggested the diagnosis of omental torsion and necrosis. At surgery, the greater omentum and part of the transverse colon were incarcerated in a small diaphragmatic hernia of the Morgagni type.