The Authors report a rare case of perforated diverticulitis of the cecum. The patient was a 68-year-old man who was referred to the Authors attention with the classic symptoms of acute appendicitis. During laparotomy a perforated "omentum-sealed" diverticulum was found on the lateral wall of the cecum, whereas the appendix appeared to be completed unaffected. A right hemicolectomy was performed. The Authors analyse the similarities and peculiarity of the case. Special attention is drawn to the problems of differential diagnosis raised by this pathology. A preoperative diagnosis is arduous because the disease is difficult to distinguish from acute appendicitis and may be even difficult to distinguish it intraoperatively from a carcinoma of the cecum. There is no characteristic clinical pattern pointing to this diagnosis. Diagnostic maneuvers are usually unrewarding. Right hemicolectomy is a safe procedure when the diagnosis is doubtful.