Lung volume reduction surgery (LVRS) is performed to alleviate dyspnoea of selected patients with severe pulmonary emphysema, and to improve their pulmonary function, performance in daily activity and quality of life. By resection of targeted emphysematous lung tissue, the achievable changes in pulmonary function consist of: 1) an increase in expiratory flow rate and airway conductance; 2) a reduction in hyperinflation accompanied by an augmentation in vital capacity; and 3) possibly, an improvement in gas exchange. Recent studies indicate that these changes are attributable to an increase of the lung's elastic recoil pressure. The consequences of an augmented recoil pressure consist of: 1) a reduction of pulmonary hyperinflation together with an amelioration of diaphragm and chest wall mechanics; 2) larger driving pressures; and 3) better airway stability. The combination of these factors is responsible for the improved pulmonary mechanics.