Which therapy could improve, or at least stabilize, the severe PH observed in some COPD patients? In patients with usual levels of PAP (< 35 mm Hg), it is generally accepted that there is no need for specific therapy. Most of these patients are markedly hypoxemic, and, accordingly, they are given long-term oxygen therapy (LTOT). Long-term oxygen therapy administered for > 15 h per day, in markedly hypoxemic patients (Pao2, < 55 to 60 mm Hg) has been shown to improve17–18 or, at least, to stabilize19–20 pulmonary hemodynamics, but all of these studies have included a great majority of patients with mild-to-moderate PH (20 to 35 mm Hg). In patients with severe PH, oxygen therapy may prove to be insufficient to stabilize PH or to reduce its progression, particularly in the presence of a true pulmonary vascular disease that is somewhat similar to idiopathic PH. Consequently, other therapies must be proposed, and lung transplantation could be a good choice in some patients, but indeed it cannot be proposed to all patients. Therapy with pulmonary vasodilators and antiproliferative drugs, including prostanoids,21endothelin receptor antagonists,22and phosphodiesterase inhibitors,23 have given promising results in the treatment of pulmonary arterial hypertension (mainly idiopathic pulmonary arterial hypertension) with regard to survival, symptoms (dyspnea), quality of life, and pulmonary hemodynamics. They could be tested in COPD patients with severe PH as more as these patients share some characteristics with patients with idiopathic pulmonary arterial hypertension. There are very few of those patients, and the possibility of a multicentric controlled study should be considered.