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BACKGROUND Pulmonary hypertension in chronic obstructive pulmonary disease (PH-COPD) is a poorly investigated clinical condition. RESEARCH QUESTION Which factors determine outcome of PH-COPD? STUDY DESIGN AND METHODS We analyzed the characteristics and outcome of patients enrolled in the COMPERA registry with moderate or severe PH-COPD as defined during the 6th PH World Symposium who received medical therapy for PH and compared them to patients with idiopathic pulmonary arterial hypertension (IPAH). RESULTS The population included incident patients with moderate PH-COPD (n=68), severe PH-COPD (n=307), and IPAH (n=489). PH-COPD subjects were older, predominantly male, and treated mainly with phosphodiesterase-5 inhibitors. Despite similar hemodynamic impairment, patients with PH-COPD had a worse 6-minute walking distance (6MWD) and more advanced World Health Organization functional class (WHO FC). Transplant-free survival rates at 1, 3 and 5 years were higher in the IPAH group than in the PH-COPD group (IPAH 94%, 75%, 55%, vs PH-COPD 86%, 55%, 38%; p=0.004). Risk factors for poor outcomes in PH-COPD were male sex, low 6MWD and high pulmonary vascular resistance (PVR). In patients with severe PH-COPD, improvements in 6MWD by ≥30m or improvements in WHO FC after initiation of medical therapy were associated with better outcome. INTERPRETATION Patients with PH-COPD were functionally more impaired and had a poorer outcome than patients with IPAH. Predictors of death in the PH-COPD group were sex, 6MWD and PVR. Our data raise the hypothesis that some patients with severe PH-COPD may benefit from PH treatment. Randomized, controlled studies are necessary to further explore this hypothesis.