An adenocarcinoid of the cecum is a tumor that has seldom been reported in the literature. Its has the histologic features of both an adenocarcinoma and a carcinoid tumor. However, the malignancy potential and the prognostic behavior are still unclear. We treated one patient with this unusual tumor. A 64-year-old man was admitted with a complaint of right lower quadrant abdominal pain for 2 months. On colonoscopy and histological examination, the patient was diagnosed as having a cecal adenocarcinoma. A radical right hemicolectomy was done. Postoperative histologic analysis revealed that the tumor was composed of well-differentiated adenocacinoma and carcinoid components. Lymph node metastases were found in the three lymph nodes with only the carcinoid component.