Chronic hepatitis B (HBV) infection is seen in 400 million persons worldwide. HBV is transmitted vertically or horizontally by infected blood and body fluids. An effective vaccine exists. Most children develop a chronic HBV infection if infected early in life. They are often in an immune-tolerant phase with no indication for antiviral treatment. Antiviral treatment with interferon or a nucleotide analogue is a possibility if the HBV infected child develops into a phase of immune activation. HBV infection can lead to liver cirrhosis and hepatocellular carcinoma.