Additional Study Information: This research is being done to look at how a medicine called Losartan helps people with Chronic Obstructive Pulmonary Disease (COPD) with emphysema, a disease of the lungs. COPD is often caused by cigarette smoking. It includes the symptoms of emphysema and chronic bronchitis. Although some medications for COPD reduce symptoms and prevent exacerbations, few medications have been shown to reduce the damage to the lungs in people with COPD. Losartan is a medicine used for treatment of high blood pressure. Losartan has been shown to slow damage to the lungs caused by COPD in animals. We would like to find out if taking Losartan can slow the damage to lungs caused by COPD. We will use images of participants lungs taken with high resolution computed tomography (HRCT) to measure changes in the lung. We also want to find out if Losartan has effects on blood and breathing tests. We are looking for men and women who are at least 40 years of age, and are current or former smokers.