Background and Aims: Confection eventuality of HIV and HBV infection and having common transmission ways has turned Hepatitis B into a major health concern among HIV positive cases. The increasing number of HIV infected patients and their relevant problems, especially opportunistic infections, demands for Hepatitis B vaccination. This study therefore was conducted to evaluate the immune response against hepatitis B vaccine and related factors among HIV positive cases and probable approaches to improve its level.Methods: In this cross -sectional study, 169 HIV positive cases who were Kermanshah's Behavioral Disease Counseling Center's clients, with negative HBsAg and HBcAb ,were vaccinated against hepatitis B virus with a 20μg of recombinant HBsAg at 0-1-6 month schedule in deltoid region. A month after the last shot, their HBsAg titer was measured. Titers higher than 10 Iu/ml were considered as a suitable immune response. Data included in this study were: age, gender, CD4 count, antiretroviral treatment history, hepatitis C confection and injecting drug abuse. Then these data were analyzed through X2 test.Results: Among 169 under study cases, immune response was overally 52.7% and this rate was 51.9% for males and 66.7%for females (P=0.313). Immune response was 54.3%, 44.3%, 45.3% in CD4 count>500, 200-499, and <200/mm3 respectively (P=0.039). In cases with and without antiretroviral treatment the immune response was 81.8% and 50.6%, respectively (P=0.045%).Conclusions: In this study the CD4 count and history of antiretroviral therapy correlation with immune response level was significant, but other factors like age, HCV co-infection, drug abusing, and gender were ineffective factors in immune response to HBV vaccine. Therefore, early vaccination among cases with higher CD4 count and cases under antiretroviral treatment seems necessary.