In a retrospective study 243 pelvic CTs in patients with acute sigmoid diverticulitis and elective resections were analyzed. A statistical correlation of radiological and histological findings was performed. The sensitivity of the CT in diagnosing sigmoid diverticulitis was 97.5%; the overall accuracy of the pelvic CT was 97.1% in acute diverticulitis. For the contrast enema the sensitivity was 71.6% and the accuracy rate ranked 71.3%. The pelvic CT in patients with clinical suspicion of acute sigmoid diverticulities is well suited for a primary diagnostic tool and can precisely show the extraluminary extension of the inflammation.