Methods and compositions are provided for diagnosing lung cancer in a mammalian subject by use of three or more selected genes, e.g., a gene expression profile, from the peripheral blood mononuclear cells (PBMC) of the subject which is characteristic of disease, a stage of the disease, or enables prognosis of recurrence of disease. The gene expression profile includes three or more genes of Table I, Table II, Table III, Table IV, Table V, Table VI or Table VII herein. Detection of changes in expression in the selected genes forming the gene expression profile from that of a reference gene expression profile are correlated with non-small cell lung cancer (NSCLC). One composition for use in such diagnosis includes three or more PCR primer-probe sets, wherein each primer-probe set amplifies a different polynucleotide sequence from the gene expression profile. Another composition for similar use contains a plurality of polynucleotides immobilized on a substrate, which probes hybridize to three or more gene expression products from genes in the gene expression profile. Still another composition involves detection of the protein expression products of genes from the gene expression profile.