Hepatitis B and C are diseases characterized by a high global prevalence, complex clinical course and limited efficacy of currently available antiviral therapy. Hepatitis B: local factors have a significant influence not only on the disease prevalence but also on the disease course. Vertical transmission of the infection in the areas of high prevalence results in perinatal infection, which universaly leads to the development of chronic disease. Factors associated with an increased risk of cirrhosis are older age, persistent viremia, coinfection with HCV, HDV and HIV, and consumption of alcohol, while the role of viral genotype is uncertain. Predictors of HCC development in cirrhotic liver are older age, male sex, alcohol abuse, exposure to aflatoxin, coinfection with HCV and HDV, continuously active inflammation, and potentially viral genotype. Survival predictors in cirrhotic patients are age, serum albumin, platelet count and splenomegaly as a reflection of portal hypertension. Hepatitis C: the risk of cirrhosis is low. Risk factors for cirrhosis are infection in older age, alcohol abuse, and coinfection with HBV and HIV. Obesity has negative impact on treatment efficacy.