Chronic obstructive pulmonary disease (COPD) is an inflammatory disease characterized by the progressive deterioration of pulmonary function and irreversible airway obstruction. Investigations of the molecular pathogenesis of COPD have not yet provided complete answers to the mechanisms that determine the onset and progression of this illness. Therefore, therapeutic choices are limited and new strategies are needed to prevent, manage and treat this disorder. In particular, the application of complementary approaches, including gel- and liquid chromatography mass spectrometry-based proteomic techniques on sputum and/or bronchoalveolar lavage may provide a better understanding of the proteome differentially expressed by COPD patients in the course of the disease. The identification of appropriate and reliable biomarkers is, thus, an essential step for the diagnostics and treatment of these patients.