A 27-yr-old female with a 6-month diagnosis of idiopathic pulmonary arterial hypertension (PAH) confirmed elsewhere was referred to our centre with worsening dyspnoea. On examination, the patient had low systemic oxygen saturation despite high oxygen flow and reduced exercise capacity. Haemodynamics were indicative of severe pre-capillary PAH. High-resolution computed tomography revealed diffuse ground-glass opacity with thickening interlobular septa, and haemosiderin-laden macrophages were identified by bronchoalveolar lavage. Based on clinical and diagnostic findings, the patient was re-diagnosed with pulmonary veno-occlusive disease (PVOD). Treatment with high-dose diuretics and the endothelin-receptor antagonist bosentan improved the patient's exercise capacity, haemodynamics and quality of life. However, 1 yr later there was a progressive, slow deterioration in the patient's functional capacity and oxygen saturation, and inhaled prostanoid and oxygen therapy were initiated. Despite some subjective improvements, the patient's haemodynamics and oxygen saturation continued to decline and she underwent lung transplantation. This case emphasises that PVOD is an under-recognised and often misdiagnosed form of pulmonary hypertension. Therefore, accurate diagnosis of PVOD requires comprehensive clinical and diagnostic work-up. While lung transplantation remains the treatment of choice for patients with PVOD, targeted therapies for PAH in addition to high doses of diuretics merit evaluation.