To investigate the relationship between HBV lamivudine resistance and HBV genotypes or basic core promoter (BCP) mutations. The common coated probes were synthesized according to the conserved regions of the preC gene of hepatitis B virus (HBV). Different colorized probes were chosen from the sequences of different genotypes of HBV (A to F), BCP and YMDD wild types and mutants, respectively. HBV DNA levels, HBV genotypes, BCP and YMDD resistants were analyzed by PCR microplate hybridization ELISA at the zero and 6th month after the patients were treated with lamivudine. HBV genotyping results showed that HBV types B, C, D accounted for about 30%, 36% and 23% patients respectively. Thirteen BCP mutations (type B in 1 patient, type C in 8 and type D in 4) were found before treatment with lamivudine. HBV DNA levels were lower than 100 pg/ml in 2 patients and higher than 100 pg/ml in 11. 9.4% of the HBV patients (5/43; type C in 3 and type D in 2) showed YMDD resistants and 4 BCP mutations at the same time. Oral treatment of lamivudine decreases the level of serum HBV DNA. The appearance of HBV YMDD resistants is related to certain HBV genotypes, and most of them are BCP mutations.