Pulmonary hypertension can occur as an isolated disease affecting the lung vessels only, in association with underlying hypoxic lung disorders or due to chronic thromboembolic disease. Regardless of the underlying disease, chronic cor pulmonale is associated with progressive clinical deterioration and a poor prognosis in most cases. The aim of specific therapies for pulmonary hypertension is to reduce pulmonary vascular resistance and thereby improve right ventricular function. Currently three classes of drugs (prostanoids, endothelin receptor antagonists, phosphodiesterase 5 inhibitors) are approved for the treatment of pulmonary arterial hypertension (PAH) in a defined patient population (group I according to the recent WHO classification). However, these medications may also lower pulmonary vascular resistance in patients with associated lung diseases (e.g. chronic obstructive pulmonary disease or lung fibrosis) and significant pulmonary hypertension, for whom these drugs are not yet approved. As non-selective vasodilators may induce gas-exchange disturbances, which preclude their long-term use in these patients, such substances should be avoided in the hypoxemic patient. In this article we provide an update of the current understanding of hypoxia- and non-hypoxia-related pulmonary hypertension, addressing both the pathophysiological understanding of different disease aetiologies as well as the therapeutic options currently available.