We identified candidate protein biomarkers to distinguish lung adenocarcinomas from benign nodules. We employed shotgun proteomics using a multidimensional peptide separation approach coupled to tandem mass spectrometry (LC-MS/MS) to characterize proteomes of a collection of 34 benign lung nodules. The benign lung nodule inventories were compared to inventories from early stage lung adenocarcinomas, from 24 patients with non-adjuvant treatment following the resection, and to inventories from normal tissue collected from 10 patients as bronchial and alveolar epithelium to identify biomarkers.We developed PRM assays to quantify a subset of 43 candidate biomarker proteins via 170 tryptic peptides in a single LC-PRM-MS run using a validation cohort of 20 benign nodules, 20 adenocarcinoma, and 20 normal lung tissues.