Objectives: the objective of this study was to detect drug-resistant mutations on polymerase gene (P) of the hepatitis B virus (HBV) from patients with chronic hepatits B in Northern Vietnam. Material and methods: a total of 198 serum samples from patients with chronic hepatitis B including 106 male and 92 female, aged 18 to 64, were analyzed by PCR and sequencing to identify anti-HBV drug resistant mutations. Results: among the genotypes of the samples, there were only 2 genotypes detected: genotype B was predominant (145/198, 73.23 percent), and genotype C (53/198, 26.77 percent). The proportion of patients with HBV resistance mutations was 82/198 (41.41 percent). Among of patients with detectable HBV mutations, the authors found only 5 mutations which were M204I (3/198, 1.52 percent), A181T (1/198,0.5 percent), S85I/F/A (7/198,3.5 percent), L80I (1/198, 0.5 percent) and V207M/L (62/198, 31.31 percent) that may resist to anti-HBV drugs such as Lamivudine, Adefovir, Entecavir, Telbivudine, and Emtricitabine. In addition to these mutations, the authors also discovered some novel.