Isolated inflammatory alterations of the greater omentum are rare diseases. Since the preoperative diagnosis is difficult these changes are usually ascertained upon laparotomy. Between 1999 and 2001 four patients (44-88-years-old, 2 males) underwent laparotomy for an inflammatory tumor mass or an acute abdomen, respectively. C-reactive protein was elevated in all cases. In two cases a primary torsion of the greater omentum was found, in the other two a paracolic pseudotumorous omentitis. Resection of the diseased omental parts led to complete recovery. Torsion of the greater omentum and omentitis cause abdominal symptoms with an inflammatory component that often mimics other more common diseases such as acute appendicitis and urges laparotomy. Partial omentectomy is the therapy of choice.