Objectives: The best outcomes from lung volume reduction surgery (LVRS) are obtained in patients with heterogeneous, upper-lobe predominant emphysema. An anatomical assessment of heterogeneity is made by computed tomography in most centres. We have preferred an assessment of "physiological" heterogeneity using radionuclide scintigraphy, calculating the percentage of total lung perfusion in the apical one-third of the operated lung: the Q score. We have analysed the predictive value of this method.