The aim of the present study was to compare the decline of HBV DNA during peginterferon (PEG-IFN) therapy with spontaneous HBV DNA decline in placebo-treated patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B. A total of 136 patients who participated in a randomized trial were treated with PEG-IFN alfa-2b for 52 weeks. These patients were compared with 167 patients who received a placebo for 48 weeks using linear mixed regression analysis. Response was defined as loss of HBeAg at the end of treatment (EOT). Overall, decline of HBV DNA at the EOT was significantly greater in the PEG-IFN group than in the placebo group (mean decline 2.3 log vs. 1.0 log, P < 0.001) and varied according to HBV genotype. Viral suppression was greater in the PEG-IFN group from week 4 throughout the entire treatment period (P < 0.001). The response rate was 32% for the PEG-IFN group and 11% for the placebo group (P < 0.001). Among responders, HBV DNA decline was greater for patients treated with PEG-IFN than with a placebo: the mean difference in HBV DNA decline was 0.7 log (P = 0.001) at 4 weeks and 2 log (P < 0.001) at the EOT. ALT flares (>5 times the upper limit) were associated with a greater HBV DNA decline during PEG-IFN. In conclusion, PEG-IFN therapy resulted in a greater HBV DNA decline in positive HBeAg patients than a placebo. The decline of HBV DNA was greater in patients with HBeAg loss or who exhibited an ALT flare during PEG-IFN than in patients with spontaneous HBeAg loss or flares during placebo therapy. J. Med. Virol. 83:1917–1923, 2011. © 2011 Wiley-Liss, Inc.