An unusual case of smoking-related centrilobular emphysema with normal spirometry. A 64-year-old man presented with severe dyspnoea and respiratory failure. Pulmonary function and mechanics were normal except for a marked reduction in diffusing capacity of the lung. High-resolution CT scan showed diffuse centrilobular emphysema also involving lower lobes. Pulmonary embolism, cardiac or pulmonary shunt and immunopathologically based vasculitis were excluded. Pulmonary pressure was at the upper limit of normality but within few months he developed a severe pulmonary hypertension. Although spirometry is the only physiologic measure recommended by the updated Global Initiative for Chronic Obstructive Lung Disease guidelines for confirming the diagnosis it should be recognized that diffuse emphysema may occur with only abnormalities in gas exchange without airflow obstruction. The identification of different phenotypes within COPD is important for understanding disease heterogeneity and progression.