Chronic obstructive pulmonary disease (COPD) is a complex genetic disorder in which environmental factors, such as tobacco smoke, interact with genetic susceptibility to cause disease. Airway obstruction in COPD is due to an exaggerated inflammatory response that ultimately destroys the lung parenchyma (emphysema) and increases airway resistance by remodeling the airway wall. Until recently, assessment of these disease processes required the examination of resected tissue. However, computed tomography (CT) now allows researchers to measure the structure of the lung parenchyma and airway wall without having to remove the tissue. This review describes some of the new CT techniques for quantitative assessment of lung structure. These techniques are extremely important to study the pathogenesis of COPD as well as differentiate patients with predominantly emphysema disease from those with airway wall remodeling, and to assess the effects of therapeutic interventions.