The invention relates to the use of Roflumilast, Roflumilast-N-Oxide or a pharmaceutically acceptable salt of either for the treatment of pulmonary hypertension. The invention additionally relates to the use of Roflumilast, Roflumilast-N-oxide or a pharmaceutically acceptable salt of either in combination with a PDE5 inhibitor or a pharmaceutically acceptable salt thereof for the treatment of pulmonary hypertension.