THE DEVELOPMENT of pulmonary hypertension (PH) is often observed in advanced chronic obstructive pulmonary disease (COPD) and indicates a poor prognosis, with a 5-year survival rate of 20-36%. 1,2 PH primarily occurs in COPD patients with severe hypoxaemia; fortunately, however, the PH is typically mild. 3 Hypoxaemia increases pulmonary artery pres- S U M M A R Ysure (PAP) through hypoxic pulmonary vasoconstriction and vascular remodelling. 4 However, there is a poor correlation between lung function parameters and PAP, suggesting that factors other than airway obstruction and/or loss of alveolar surface may play a role in its aetiology.Recent studies have shown that a proportion of patients with only moderate airway obstruction have severe PH. 5,6 Disproportionate PH in COPD patients seems best defi ned as at least moderate elevation in SDL and YMO contributed equally to this article.