Pulmonary hypertension (PH) is a frequent complication of chronic obstructive pulmonary disease (COPD) highly correlated with the prognostic disease. In advanced stages, pulmonary vascular remodeling together with the hypoxia induced vasoconstriction represents the main factors responsible for PH. However, recent studies have demonstrated that structural anomalies of pulmonary arteries may be already evident in the initial stages of COPD, which usually lack hypoxemia. The mechanisms underlying these structural and functional alterations of pulmonary vessels are related to the deleterious effects of different components present in the cigarette smoke and to the inflammatory changes occurring in these patients. The smoking induced lesions of pulmonary arteries endothelium, either direct or secondary to the subjacent inflammation, predispose these patients to the farther action of hypoxia. Taking in account all these observations, it seems that pulmonary vascular remodeling associated to COPD follows, at least partially, a similar pathogenesis as that described within the primary PH, where the endothelial dysfunction plays the essential role.