[en] In this paper we review the current knowledge on pulmonary hypertension (PH) occurring in COPD. PH is defined as a mean pulmonary arterial pressure at rest greater than 20 mmHg measured by right heart catheterisation. PH is usually present during exercise before appearing at rest. PH in COPD increases the risk of hospitalisation and darkens the disease prognosis. Chronic hypoxemia is the major contributor to PH, but remodelling of arterial wall and mechanical factors such as hyperinflation also play a role. Transthoracic echocardiography is the most useful non invasive investigation, but right heart catheterisation is necessary to ascertain the diagnosis. Long term 02 supplementation is the basis of the treatment while vasodilatators may worsen hypoxemia.