Meckel's diverticulitis is a rare disease. In addition to physical examination, abdominal ultrasound can help to pinpoint the diagnosis. By presenting a case report we would like to demonstrate the typical ultrasonographic findings in acute Meckel's diverticulitis and differentiate it from acute appendicitis. A 60-year-old patient was admitted to our hospital with the diagnosis of acute appendicitis. Abdominal ultrasound was performed and a blind ending, liquid-filled segment of small bowel in the right lower quadrant of the abdomen found. This segment was not compressible, no peristalsis was evident, nor was there any anatomical association with the cecum. Locally we found free fluid and hints of inflamed mesenteric fatty tissue. A perforated Meckel's diverticulum was diagnosed and confirmed intraoperatively. The major ultrasonographic difference between an inflamed Meckel's diverticulum and acute appendicitis is its anatomical location. In contrast to the appendix there is no association with the cecum. A diameter of up to 40 mm and a well-defined wall of small bowel with 3 definite layers visible by ultrasound may help to distinguish between a Meckel's diverticulum and the appendix.