Hepatitis viruses, particularly HBV and HCV, are major causes of hepatocellular carcinoma worldwide, due to the induction of chronic liver disease and of cirrhotic transformation of the liver. Cirrhosis certainly represents the most important link between chronic viral hepatitis and HCC. Under these circumstances, risk of HCC development in chronic HBV and HCV infection is strictly dependent on the propensity to cirrhotic transformation. Intervention of other, more direct, molecular events induced by the virus itself are suspected, particularly for HBV which is able to integrate into the host genome, but not yet incontrovertibly proved.