Cigarette smoke has been widely investigated in terms of epidemiological and pathological studies in relation to human lung diseases. In this study, we conducted a proteomic analysis to characterize the differential protein expression in lung tissue of rats exposed to cigarette smoke. Wistar rats were exposed to cigarette smoke twice a day, 30 min each for 1, 2 and 4 months, respectively. The total protein of lung tissue was extracted for two-dimensional electrophoresis (2-DE) and analyzed with ImageMaster 2D Platinum software. A total of 28 differentially expressed proteins between the control and the smoke-exposed groups were screened and of which 18 were identified by matrix assistant laser desorption ion-top of flight-mass spectrometry (MALDI-TOF-MS) or MALDI- TOF-TOF analysis, revealing 10 up-regulated and 8 down-regulated proteins. The up-regulated expression of two proteins, receptor for advanced glycation endpoints (RAGE) and thioredoxin (Trx), were validated by immunoblotting and found to be consistent with the proteomic analysis. The results presented in this study demonstrate the identification of proteomic pattern as an early indicator of lung damages induced by cigarette smoke. The differentially expressed proteins may be applied as exposure biomarkers in future experimental as well as epidemiologic investigations upon confirmation by a greater sample size and more validate study design for the proteomic research.