OBJECTIVE We investigated the unsettled issue of whether seropositivity for antibody to hepatitis B core antigen (anti-HBc) affects characteristics of hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC). METHODS Antibody status was determined by enzyme immunoassay in 243 patients with this cancer, and associations with clinicopathologic characteristics and outcome were analysed. Serum hepatitis B virus (HBV) DNA was determined by real-time polymerase chain reaction. RESULTS Of 235 patients with unequivocal serologic status, 142 were seropositive and 93 were seronegative. Clinicopathologic characteristics and overall cumulative survival rates were comparable between the two groups. However, seropositivity tended to predict poor outcome for patients in Child class B or C (P=0.068), those in tumour-nodes-metastasis-based stage 3 or 4 (P=0.081), those with tumours exceeding 25 mm (P=0.068), and those with a past history of clinical liver disease (P=0.088). Multivariate analysis identified serum albumin, portal vein tumour thrombosis, and tumour size as independent determinants of survival. Serum HBV DNA was below 1.7 log copies/ml in all 40 patients tested. CONCLUSIONS Overall, the clinical features of HCV-HCC were unaffected by seropositivity for anti-HBc. Seropositivity tended to worsen prognosis for subgroup with poor hepatic reserve or advanced tumours.