The authors report a case of abdominal aortic aneurysm surgically treated. At surgical exploration an ileal diverticulum was discovered. A 15 cm ileum tract was hyperemic and oedematous. The abdominal aortic aneurysm was resected and an aorto aortic graft implanted. The retroperitoneal space was carefully closed and then the diverticulum resected and an end-to end intestinal anastomosis performed. An etiological review of this pathology was done identifying two possible causes: true and false diverticula. The true diverticulum is a congenital lesion involving the 3 layers of the intestinal wall. On the contrary the false diverticulum is acquired and generally develops on the mesenteric site due to a pulsion mechanism. The wall involves the mucosa and serosa layers only. Diagnosis is often done during abdominal exploration for other cause (as in our case) or for complicated diverticula. Preoperative radiologic diagnosis is rare and doesn't always require surgical treatment.