Positron emission tomography (PET) using F-18 fluoro-2-deoxy-d-glucose (18F-FDG) is now well established as a noninvasive diagnostic tool for the detection of a variety of malignant tumors. However, in the case of hepatocellular carcinoma (HCC), several investigators have reported controversial conclusions and an inadequate sensitivity for PET (50-55%). Nevertheless, a high positive rate of 18F-FDG accumulation has been reported in patients with high-grade HCC and in those with markedly elevated alpha-fetoprotein (AFP) levels. Here, we retrospectively reviewed 38 HCC cases that received liver transplantation (LT) at our center between November 2000 and July 2004 and underwent whole-body PET imaging. 18F-FDG uptake was assessed in the liver, and its prognostic significance was investigated. Of 38 patients enrolled, 13 patients had positive PET scans for a liver tumor. When we analyzed the association between tumor factors and PET+ (greater PET lesion uptake) in the liver, preoperative AFP level and vascular invasion were found to be significantly associated with PET+ (P = 0.003 and P < 0.001, respectively). However, the association between histological grade and PET+ findings did not reach statistical significant difference (P = 0.074). Moreover, the 2-year recurrence-free survival rate of PET− patients was significantly higher than that of PET+ patients (85.1% vs. 46.1%) (P = 0.0005). Of 6 PET+ patients who met the Milan criteria, 4 patients (66.7%) had recurrence, but all 20 PET− patients who met the Milan criteria were recurrence free. Thus, PET imaging could be a good preoperative tool for estimating the post-LT risk of tumor recurrence, because histological grade and vascular invasion cannot be determined preoperatively. Importantly, our results indicate that tumor recurrence can be highly anticipated for PET-imaging-positive HCC patients who satisfy the Milan criteria. We advise that PET+ HCC patients be selected cautiously for LT. Liver Transpl, 2006. © 2006 AASLD.