The invention relates to a double-stranded ribonucleic acid (dsRNA) for inhibiting the expression of a Hepatitis B Virus gene. The invention also relates to a pharmaceutical composition comprising the dsRNA or nucleic acid molecules or vectors encoding the same together with a pharmaceutically acceptable carrier; methods for treating diseases caused by Hepatitis B Virus infection using said pharmaceutical composition; and methods for inhibiting the expression of a Hepatitis B Virus gene in a cell.