This randomized, 2 x 2 factorial, parrallel group study will compare the efficacy and safety of 48 versus 96 weeks of peginterferon alfa-2a [Pegasys], with or without entecavir, in patients with HbeAg negative chronic hepatitis B. Patients will be randomly allocated to receive Pegasys (180mcg subcutaneously weekly) for 48 weeks plus placebo (group A) or entecavir (0,5mg orally daily, group B) during weeks 12-36, or Pegasys (180mcg subcutaneously weekly) for 96 weeks plus placebo (group C) or entecavir (group D) during weeks 12-36. Anticipated time on study treatment is 48 or 96 weeks, with a follow-up of 48 weeks. Target sample size is <500 patients.