This article provides a brief overview of the important issues influencing the effective use of quantitative X-ray computed tomography (QCT) in the assessment of the lung parenchyma in patients or research subjects with chronic obstructive pulmonary disease (COPD). This effort builds on an earlier workshop that was done in 2001. The pathologic appearance of emphysema is briefly reviewed. CT scanner, CT phantom, and CT image acquisition parameters are discussed that are important in obtaining high quality CT images of the lungs for image quantitation. Data storage, data transfer and data archival issues are reviewed. Current image processing techniques to derive meaningful quantitative measures of emphysema are also discussed.