Matrix metalloproteinase-9 (MMP-9) expression is upregulated in various diseases, including lung cancer. However, the role of MMP-9 genotype in lung cancer susceptibility remains uncertain. This study aimed to clarify the contribution of MMP-9 promoter rs3918242 genotypes to the risk of lung cancer in Taiwan. The MMP-9 rs3918242 genotypes of 358 lung cancer patients and 716 healthy controls were determined using polymerase chain reaction-restriction fragment length polymorphism methodology. Individuals carrying the variant CT or TT genotype of MMP-9 rs3918242 did not demonstrate an increased risk of lung cancer compared to wild-type CC carriers odds ratio (OR)=1.11 and 1.85, 95% confidence interval (95%CI)=0.82-1.48 and 0.91-3.76; p=0.5541 and 0.1280, respectively. Moreover, individuals carrying the T allele did not show a higher lung cancer risk compared to those with the C allele (OR=1.21, 95%CI=0.95-1.54, p=0.1444). However, a significant association was observed between the MMP-9 rs3918242 TT genotype and lung cancer risk among non-smokers (OR=5.48, 95%CI=1.31-22.89, p=0.0181). The presence of the TT genotype for MMP-9 rs3918242 may indicate an elevated risk of lung cancer among non-smokers.