Background. Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. The progno-sis of patients with HCC is generally poor, and life expectancy is difficult to predict because of various factors. The purpose of the present study was to investigate the relationships between FDG PET parameters and other parameters that may influence the prognosis of patients with HCC. Materials and methods. We conducted a retrospective study on 26 patients who underwent dual-time-point FDG PET imag-ing before treatment between June 2010 and April 2016 at Nagasaki University Hospital. The SUVmax, SUVpeak, TLG, and MTV of tumors and the SUVmean of the liver were assessed on PET images using Metavol software. All statistical analyses were performed using JMP Pro11 software. P-values of < 0.05 were considered to be significant. Results. Log AFP and log PIVKA II showed strong relationships between many FDG parameters. Several types of therapy performed before the introduction of FDG PET showed some relationships but few for FDG parameters. Relationships be-tween AFP, PIVKA II, and therapy were only found between log AFP and the number of transarterial chemoembolizations. The results of the event-free survival analysis showed that patients with larger tumors on PET images had a poorer prognosis. Conclusion. Relationships were observed between FDG PET parameters and AFP and PIVKA II levels, which affect patient prognoses. Based on the present results and previous findings, the combination of FDG parameters with serum AFP and PIVKA II levels may be useful for predicting the outcomes of patients with HCC.