OBJECTIVE The effect of entecavir (ETV) therapy on viral suppression and hepatic function in hepatitis B virus (HBV) patients with decompensated cirrhosis has not been established. We evaluated ETV as first-line monotherapy in these patients. METHODS We consecutively enrolled 70 HBV-infected patients with decompensated cirrhosis primarily treated with 0.5mg/day ETV, and evaluated the clinical outcomes by intention-to-treat analyses. We also compared the virological responses of 55 patients treated for 12 months (decompensated group) with those of 144 chronic hepatitis or compensated cirrhosis patients (compensated group). RESULTS The cumulative transplantation-free survival was 87.1% at 1year. ETV treatment for 12 months resulted in improved Child-Turcotte-Pugh (CTP) and model for end-stage liver disease (MELD) scores. Sixty-six percent (36/55) of patients achieved CTP class A and 49% (27/55) showed improvement in the CTP score of 2 points after 12 months of ETV. The 1-year cumulative rates of HBV DNA negativity and HBeAg loss were 92.3% and 54.0%, respectively, by intention-to-treat analysis. The rates of HBV DNA negativity, HBeAg seroconversion/loss and ALT normalization at month 12 were similar for the decompensated and compensated groups. Cox regression analysis showed that pretreatment HBeAg seropositivity was a negative predictor of HBV DNA clearance during ETV therapy (hazard ratio, 0.514; 95% confidence interval 0.367-0.719; p<0.001). CONCLUSIONS One-year initial ETV therapy was similarly effective in both compensated and decompensated liver disease HBV patients. In addition, it improved underlying liver function in decompensated patients.