It is pointed out that there can be a discrepancy between the effect diagnosed by radiographic imaging and that by histological examination, when we treat patients with liver metastases of colorectal cancer by a transient hepatic arterial chemoembolization. We report a case of liver metastases of rectal cancer in which F-18-fluorodeoxyglucose positron emission tomography (FDG-PET) was useful for evaluating the therapeutic efficacy for transient hepatic arterial chemoembolization. A 58-year-old man with synchronous liver metastases (H2) of rectal cancer underwent a low anterior resection, a partial hepatectomy, cholecystectomy, and ligation of the gastroduodenal artery. After these operations, the patient received 6 hepatic arterial injections with degradable starch microspheres (300-600 mg), adriamycin (30 mg), and mitomycin C (10 mg) for the remaining metastatic lesion (S7). Although abdominal CT scan revealed a partial response, FDG-PET did not show any abnormal deposits. Hepatic posterior segmentectomy was performed 7 months after the first operation. Histological examination did not show any viable tumor cells in the resected specimen.