 Entecavir has a higher potent antiviral efficacy and a lower drug resistance rate than those of Lamivudine in nucleoside-naïve CHB patients. The switch from Lamivudine to Entecavir in patients who have undetectable hepatitis B virus DNA HBV DNA 60 IUmL may lead to more prolonged viral suppression to undetectable level by PCR method, compared to patients with continuous lamivudine treatment. The results of this study will provide a rationale for switch treatment from one antiviral to another one, especially from LAM to ETV. 