Simple tests of lung function may be misleading in the assessment of patients with interstitial lung disease. Eight patients are described with cryptogenic fibrosing alveolitis (histologically proven in four) with severe breathlessness and low gas transfer (median DLCO 32.4%, range 9.2 to 35.3%, % predicted) in whom lung volumes were preserved [median VC 98.7, range 67.5-131.1%; median TLC 92.5, range 88.1 to 121.2, (% predicted)], and in whom there was no evidence of airflow obstruction [median FEV1/FVC 84.6, range 68-116 (% predicted)]. All were current or ex-heavy smokers. Thoracic high resolution computed tomography revealed upper zone emphysema, the extent of which was not appreciated using conventional chest radiography. The atypical physiological and radiological features can be explained by coincidental cryptogenic fibrosing alveolitis and emphysema and high resolution computed tomography was valuable in the assessment of these patients.