Lung cancer in never-smokers is increasingly recognized as a disease influenced by genetic susceptibility. Aldehyde-metabolizing enzymes, including the ALDH gene family and ADH1B, play key roles in detoxifying reactive aldehydes that can damage DNA and promote oxidative stress. In this study, we will examine whether ten selected genetic variants, nine single nucleotide polymorphisms (SNPs) across five ALDH family genes and one variant in ADH1B are associated with the risk of lung cancer and its major subtypes. Limited epidemiological evidence is currently available on the association between these aldehyde-metabolizing gene variants and lung cancer. This research aims to clarify their potential contribution to the development of lung cancer, particularly among never-smokers.