Introduction: Liver cirrhosis (20-25%), hepatocellular carcinoma (1.5-3%), insulin resistance (30-40%) and type 2 diabetes (25-30%) are common complications in patients with chronic hepatitis C virus (HCV) infection; however, data are missing from Hungary. Aim: To determine the prevalence of diabetes and insulin resistance in Hungarian HCV patients; to evaluate treatment-induced metabolic changes in relation to diabetes/insulin resistance and virological response and to perform a sustained follow-up for hepatocellular carcinoma detection. Method: We enrolled 150 Hungarian HCV genotype 1 patients (mean age: 48.55 ± 8.55 years, male/female ratio: 45/55%) from 2007-2012. We analysed their baseline, week 12, and end of therapeutic follow-up (24 weeks after interferon-based therapy completion) laboratory data. We performed a 5-year follow-up (2012-2017). Results: The prevalence of insulin sensitivity, insulin resistance and diabetes was 37.4%, 35.3% and 27.3%, respectively. Insulin resistant and diabetic patients showed a decrease in fasting glucose from baseline to end of follow-up (5.47 ± 0.66 vs. 5.08 ± 0.60, p<0.001; 7.90 ± 2.67 vs. 7.04 ± 2.75, p = 0.006), as did both the sustained responder and non-responder groups. Treatment efficacy rate was poor in diabetic vs. insulin sensitive and insulin resistant groups (17% vs. 46% and 40%); insulin sensitivity was not a predictor of virological response. Three participants with diabetes were diagnosed with hepatocellular carcinoma during follow-up by regular ultrasound examinations. Conclusion: Hungarian HCV patients showed high prevalence of diabetes and insulin resistance, though antiviral therapy caused favourable changes in their carbohydrate metabolism. Antiviral therapy was less effective in diabetic patients. Follow-up ultrasound examinations are required for hepatocellular carcinoma in HCV patients, especially those with diabetes. Orv Hetil. 2019; 160(40): 1591-1602.