In lung cancer, expressive survival has not yet been achieved in non surgical stages. Non-small cell lung cancer (NSCLC) patients are treated with platinum and other drugs. To choose these agents we can actual ly define predictive biomarkers to preview therapeutic response.A literature revision was done in order to define the role of ERCC1 e RRM1 genes in the response to chemotherapy based in platinum and gemcitabine respectively. The expression of these genes is faced as a predictive marker to the chemotherapy response in patients with adenocarcinomas and squamous cell carcinomas, providing a personalized therapy.Published data supports this behaviour and is useful to individualize therapy accordingly to individual levels of ERCC1 which are modified by genetic mutations. Polymorphisms in codons 118 C/T and C8092A, seem to influence the carcinogenesis, cytostatic resistance, survival and even the prognosis.Clinical and laboratorial trials showed that high expression of RRM1 gene in NSCLC has impact in the tumoral phenotype. Patients having done surgical ressection and presenting high expression of RRM1 have better survival than those with lower expression. However, patients with advanced NSCLC and treated with chemotherapy with gemcitabine and cisplatin appear to have a poor outcome if the tumor express elevated levels of RRM1 gene.