Cytochrome P450 2D6(CYP2D6) is one of the prominent phase I metabolizing enzymes in hepatic tissue, and is responsible for metabolically activating the tobacco-specific nitrosamine such as NNK and nicotinamide to highly reactive metabolites, so it may play a role in lung cancer. The study of its biological characters, structure function and the relationship beween CYP2D6 genetic polymorphisms and lung cancer susceptibility can redound to understand the significant influence of CYP2D6 on lung cancer susceptibility. Furthermore from the point of view of interaction between gene and environment it can evaluate the lung cancer risk accurately.