Background: occult hepatitis B virus (HBV) infection is characterized by the presence of HBV infection with undetectable hepatitis B surface antigen (HBsAg). Such infections have been reported to be common in patients with chronic hepatitis C virus (HCV) infection. Objective: this study investigates the prevalence of occult HBV infection in patients with chronic liver disease by HCV.  Methods: in a cross sectional study, a toal of 3043 blood donors were screened in 2009 for the following viral markers: hepatitis C virus antibody (anti-HCV), hepatitis B surface antigen (HBsAg), and human immunodeficiency virus I/II (anti-HIV I/II). All samples negative for HBsAg and positive for anti_HCV were tested for the presence of anti-hepatitis B core antigen (anti_HBc). Results: one hundred and fort samples (4.6%) were positive for anti-HCV. Of these 140 cases, 36 (25.71%) were anti_BHc positive.  Conclusion: occult hepatitis B infections occur frequently in patients with chronic hepatitis C liver disease.