There is little information in literature about the use of hepatitis B immunoglobulin (HBIg) in recipients of bone marrow transplantation (BMT). Here, we report two children who received IV HBIg (Hepatect-CP) and lamivudine treatment during BMT course for either patient or donor hepatitis B virus (HBV) viremia. A four-year-old girl underwent a fully human leukocyte antigen-matched allogeneic BMT for thalassemia major from her mother positive for hepatitis B surface antigen (HBsAg). A 12-yr-old boy with chronic myeloid leukemia, positive for HBsAg and HBV-DNA received a fully HLA-matched allogeneic BMT from his sister in the first chronic phase of the disease. HBIg was successfully used in both cases to prevent HBV reactivation of the recipients. The results of our observations are encouraging and we suggest that HBIg in combination with lamivudine may be used in such cases especially in post-transplant early period to prevent HBV reactivation.