Half of the female patients with adenocarcinoma in East Asia are never-smokers. Proteomic analysis of tumor tissue may throw important light on the pathogenesis of this interesting subgroup of lung cancer. The cancer and adjacent normal lung tissue were taken from 21 never-smoked adenocarcinoma and profiled using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). Fifty-two proteins were significantly discriminatory between tumor and normal lung tissues. Ninety-three proteins were found to have high accuracy in discriminating between adenocarcinoma with or without smoking history. These proteins may yield new insights about the altered pathogenetic pathways of never-smoked lung cancers.