The polymorphism T6235C of CYP1A1 gene has been shown to cause high risk factor for lung cancer in Asian subjects. In this study, the polymorphism T6235C of CYP1A1 gene in 139 lung cancer patients is compared with 100 control samples by PCR - RFLP method (PCR - Restriction fragment length polymorphism). Results show that the frequency of T and C allele in lung cancer patients (75 percent, 25 percent) are different from that of the control group (84 percent, 16 percent) with p 0.05; the difference between the frequencies of T/T genotype; T/C - C/C in the lung cancer group (0.288, 0.712) and the frequencies of T/T genotype; T/C - C/C in the control group (0.36; 0.64) with P 0.05 level is statistically significant. In conclusion, the authors observed the correlation between polymorphism T6235C of CYP1A1 gene with lung cancer risk in Vietnam.