Chronic obstructive pulmonary disease (COPD) and lung cancer result in significant morbidity and mortality worldwide. In addition to the role of environmental smoke exposure in the development of both diseases, recent epidemiological studies suggests a connection between the development of COPD and lung cancer. Furthermore, individuals with concomitant COPD and cancer have a poor prognosis when compared with individuals with lung cancer alone. The modulation of molecular pathways activated during emphysema likely lead to an increased susceptibility to lung tumor growth and metastasis. This review summarizes what is known in the literature examining the molecular pathways affecting matrix metalloproteinases (MMPs) in this process as well as external factors such as smoke exposure that have an impact on tumor growth and metastasis. Increased expression of MMPs provides a unifying link between lung cancer and COPD.