A 49-year-old man was referred to the hospital with the complaints of haematochezia and weight loss. Colonoscopy and pathological needle biopsy suggested moderately to highly differentiated adenocarcinoma. The patient underwent abdominal CT examination, which demonstrated two augmented and irregular masses in the liver. However, the glucose metabolism of 18F-FDG in these two lesions was completely different. Considering the different glucose metabolism, a needle biopsy of the liver mass was performed, and the diagnosis was rectal cancer with liver metastasis and primary hepatocellular carcinoma.