Abstract: Objective To explore associations of polymorphisms of CYP1A1 and GSTM3 genes with susceptibility of lung cancer among Han population in Inner Mongolia.Methods Allele specific amplification and PCR-restriction fragment length polymorphism(PCR-RFLP) methods were used to analyze the genes polymorphisms of 324 Han patients without lung diseases and 174 Han lung cancer patients and the relationship between smoking and lung cancer was also analyzed simultaneously.Results There was no significant difference between lung cancer patients and the controls in CYP1A1 and GSTM3 with Chi-square test(P>0.05).Smokers had a 2.107 odds ratio(OR,95% confidence interval:1.44,3.080) of lung cancer compared to the controls.The risk was increased in the the subjects with CYP1A1 gene homozygous variant(Val/Val),with an OR of 1.576.There was a 2.5-fold increased risk of lung cancer among the subjects with CYP1A1 heterozygote(Ile/Val) and homozygous variant(Val/Val) and smoking.Conclusion Smoking is the risk factor of lung cancer.CYP1A1 heterozygote and homozygous variant were suspicious susceptibility factors of lung cancer.Smoking and CYP1A1 gene variant has synergistic effect on lung cancer susceptibility.There is no relationship of GSTM3 gene polymorphisms and lung cancer suscepitibility.