This review will focus on the relationship between leptin system and non-small cell lung cancer (NSCLC), in which special attentions will be paid on the expression of leption and its receptor (LepR) in peripheral blood and tumor tissues, leptin-related signal transduction pathways, the interaction between leption and regulatory T cells (Treg) and the gene polymorphisms of leptin and leptin receptor, and possibly provide new strategies for diagnosis and treatment of NSCLC. Here, LEP is linked to neoplasm.