Matrix metalloproteinases (MMPs) are zinc-endopeptidases responsible for degradation of the extracellular matrix (ECM) components including basement membrane collagen, interstitial collagen, fibronectin, and various proteoglycans, during normal remodeling and repair processes. The turnover and remodeling of ECM must be tightly regulated since excessive or inappropriate expression of MMPs may contribute to the pathogenesis of tissue destructive processes associated with lung inflammation and disease. Despite the fact that our knowledge in the field of MMP biology is rapidly expanding, the role of MMPs in the pathogenesis of lung diseases is still not clear. The aim of the present review is to present the basic principles of MMP biology and, subsequently, to focus on the clinical and experimental evidence related to MMP activity in various lung disorders, including lung cancer, pleural effusions, chronic obstructive pulmonary disease, asthma, acute respiratory distress syndrome and interstitial lung diseases.