OBJECTIVES: Intravenous drug use accounts for most of the new hepatitis C infections worldwide. Although there is an urgent need for antiviral treatment of infected intravenous drug users (IDUs), several factors compromise their treatment including lack of treatment adherence and high dropout rate. The aim of this study was to compare antiviral treatment-related problems among former IDUs to HCV-infected patients without a history of IDU. METHODS: This was a retrospective chart review of HCV-infected IDUs who received combined antiviral therapy at the Hepatology Outpatient Clinic of Szent László Hospital between 1 January 2006 and 31 December 2008. A control group of interferon treated patients with no history of IDU matched for age and sex was selected. RESULTS: Dropout rate was significantly higher in the IDU group (p = 0.016). Treatment response at the 12th week of treatment was significantly better in the IDU group (p = 0.004). Significantly more IDUs underwent antiviral treatment while in prison (p = 0.008). CONCLUSIONS: In this study higher dropout rate was found among IDUs. IDUs had a better response rate to antiviral therapy compared to controls. More attention should be paid to factors that worsen treatment adherence of IDUs - particularly lack of abstinence - in order to increase the effectiveness of antiviral therapy.