Although smoking is the most important risk factor, a significant portion of lung cancer in women occurs in non-smokers.4 Global statistics estimate that 20% of lung cancer in Western populations develops in non-smokers.1 In Korea, 38% of female non-small-cell lung cancer patients reported themselves to be non-smokers.5 Female lung cancer patients have a higher proportion of adenocarcinoma histology,6 and a higher frequency of mutations in the epidermal growth factor receptor (EGFR)7 than male lung cancer patients. This evidence concerns the gene EGFR and lung cancer.