Background/Aim: Lung cancer is the leading cause of cancer-related death and a better marker for advanced personalized therapeutic approaches, such as immunotherapies, is in urgent need. Interleukin-12 (IL-12) is a cytokine that has been reported to exhibit potent tumoricidal effects, however, the contribution of IL-12 genotypes to lung cancer is still largely unrevealed. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in IL-12A and IL-12B are associated with lung cancer in a Taiwanese population. Materials and Methods: Genotypes of 358 lung cancer patients and 716 controls were determined by the polymerase chain reaction–restriction fragment length polymorphism method. Results: The distributions of genotypic (p=0.0036) and allelic (p=0.0005) frequencies of IL-12A rs568408 demonstrated significant differences between cases and controls. In detail, the AA genotype of IL-12A rs568408 was associated with a significantly elevated risk of lung cancer compared with the GG genotype (odds ratio(OR)=2.41, 95% confidence interval(CI)=1.36-4.29, p=0.0021). No difference was observed regarding IL-12A rs2243115 and IL-12B rs3212227 genotypes between the case and control groups. In addition, the results of interaction analysis showed that the AA genotype of IL-12A rs568408 was associated with elevated lung cancer risk, especially among those with smoking habits (p=0.0043). Conclusion: IL-12A rs568404 AA genotype may contribute to the etiology and serve as a genomic determinant of lung cancer in Taiwanese, especially smokers.