Lung cancer metastasis causes 70% of an estimated 1.4 million deaths per annum. The major shortcoming in lung cancer is the tendency to have inherent or develop acquired resistance to chemotherapy. It is now evolving that such resistance might develop due to differential contribution and interaction with tumor microenvironment, stromal cells, and the extracellular matrix. The objective of the current study was to define the lung cancer tumor microenvironment. We have identified multiple tumor-infiltrating T lymphocyte subsets in patients with lung cancer, which were independent of disease stage. Functional analysis indicated high expression of the inhibitory receptors, cytotoxic T-lymphocyte-associated protein 4 (CTLA4), lymphocyte activated gene 3 (LAG3) and programmed cell death protein 1 (PD-1) in both CD4 and CD8 subsets, compared to non-malignant controls. Inhibitory receptors expressed by the tumor infiltrating T cells might mediate tolerance to tumor antigens with co-expression of these receptors exacerbating lung carcinogenesis and metastatic progression.