Three elderly patients presented with acute abdominal pain in the right lower quadrant and leukocytosis. CT-imaging of the abdomen supported the suspicion of acute appendicitis. The patients underwent appendectomy. After pathological examination, two patients were found to have a colon carcinoma. The third patient had a normal appendix; however, adenocarcinoma of the cecum was found four weeks later. The patients underwent a second operation, a right hemicolectomy, within two months. In patients older than 65 years with symptoms of acute appendicitis, colon cancer should be considered in the differential diagnosis. Distinguishing between appendicitis and colon cancer based on clinical symptoms and imaging is difficult. However, this distinction is important for the prognosis and choice of surgical treatment. If no direct evidence of malignancy is present in elderly patients with symptoms of appendicitis, a colonoscopy should be performed postoperatively to exclude colon cancer.