Occult HBV infection is characterized as a clinical form of hepatitis B in which, despite the absence of detectable HBsAg in the serum of patients, HBV-DNA is present in the serum or liver. In this study we aimed to selecting of HBsAg negative, HBcAb positive patients among plasma samples of healthy blood donors and evaluate some of the elements of humoral immunity. The results from this study showed that all examined 350 Blood donors were divided by ELISA screening tests into four studied groups, HBsAg−/anti-HBc+ 65(18.58%) and Recovery 85(24.28%), 100 (28.57%) patients and 100 (28.57%) healthy. Our results showed that the serum levels of IgG and C3 were significantly higher in patients, while IgM and C4 were not significant among the studied groups. Based on these results, it could be concluded that one possible reason that HBV was able to persist in patients in HBsAg−/antiHBc+ group was their inability to produce appropriate levels of IgG antibodies directed towards the clearance of the viral infection.