The KRAS gene mutations were significantly more frequent in adenocarcinoma patients than in other types of NSCLC (30 % adenocarcinoma, 6.9 % squamous-cell carcinoma, 13.6 % large-cell carcinoma, 14.3 % not otherwise specified (NOS) NSCLC; p = 0.0391; χ2 = 8.36), in current smokers than in non-smokers and former smokers (22.2 % non-smokers, 42.9 % former smokers, 19.2 % current smokers; p = 0.037; χ2 = 6.567) and in light smokers then heavy smokers (58.8 vs. 16.9 %; p = 0.00027; χ2 = 13.254). This evidence concerns the gene KRAS and squamous cell carcinoma.