This invention relates to the treatment of a patient's lung, for example, a lung exhibiting chronic obstructive pulmonary disease (COPD) and in particular to methods and devices for affecting lung volume reduction, preferably for achieving acute or immediate lung volume reduction following treatment. The lung volume reduction is effected by delivering a condensable vapor at a temperature above body temperature to the desired regions of the patient's lung to damage tissue therein. Blood flow and air flow to the damaged tissue region is essentially terminated, rendering the target region non-functional. Alternative energy sources may be used to effect the thermal damage to the lung tissue.