Effective hepatitis B virus control has warranted a decline in hepatitis B virus prevalence over the world with a relevant reduction in hepatitis B virus-associated delta hepatitis. However, despite the dramatic decline in hepatitis D virus infection rate, no further decrease was recorded after 2000. This cross-sectional study aims to investigate: I- The prevalence of hepatitis D virus co-infection in children with hepatitis B virus infection in Western Turkey; II- The influence of neonatal hepatitis B virus vaccination on hepatitis D virus co-infection rate; and III- The impact of co-infection on prognosis of liver disease. Serological markers of hepatitis B virus and hepatitis D virus infections were determined by ELISA in patients with chronic hepatitis during immune tolerance, immunoactive, HBeAg-negative chronic, and inactive carrier state. Delta co-infection rate was evaluated in two groups, children born before and after the national neonatal mass vaccination has started (before and after 2000). Viral load, serum alanine aminotransferase, and histological grade were evaluated in co-infected cases. Overall hepatitis delta virus infection rate was 1,76% (3/170); two patients with eAg-negative chronic hepatitis B and one patient in the immunoactive phase were infected with hepatitis D virus. Mean fibrosis score of hepatitis D virus -infected cases and hepatitis B virus -infected counterparts were 4±1,7 and 1,3±1, respectively (p: 0,006). Hepatitis D virus infection was detected in 2 out of 158 children born before and in 1 of 12 born after the neonatal vaccination program. Hepatitis B e-antibody was detected in two patients with delta co-infection (11 and 6 years old), and all mothers of delta hepatitis cases were chronically hepatitis B virus-infected. Delta hepatitis is rare among hepatitis B virus-infected children in the Western region of Turkey. Despite the success of the national vaccination program, delta hepatitis is not a vanishing disease and it has a grave prognosis due to development of early cirrhosis.