OBJECTIVE. The purpose of this study was to evaluate the relation between bronchial wall attenuation on thin-section CT images and airflow limitation in persons with chronic obstructive pulmonary disease. SUBJECTS AND METHODS. One hundred fourteen subjects (65 men, 49 women; age range, 56-74 years) enrolled in the National Lung Screening Trial underwent chest CT and prebronchodilation spirometry at a single institution. At CT, mean peak wall attenuation, wall area percentage, and luminal area were measured in the third, fourth, and fifth generations of the right B1 and B10 segmental bronchi. Correlations with forced expiratory volume in the first second of expiration (FEV1) expressed as percentage of predicted value were evaluated with Spearman's rank correlation test. RESULTS. The peak wall attenuation of each generation of segmental bronchi correlated significantly with FEV1 as percentage of predicted value (B1 third, r = -0.323, p = 0.0005; B1 fourth, r = -0.406, p < 0.0001; B1 fifth, r = -0.478, p < 0.0001; B10 third, r = -0.268, p = 0.004; B10 fourth, r = -0.476, p < 0.0001; B10 fifth, r = -0.548, p < 0.0001). The correlation coefficients were higher in peripheral airway generations. Wall area percentage and luminal area had similar significant correlations. In multivariate analysis to predict FEV1 as percentage of predicted value, the coefficient of determination of the model with the combination of percentage of low-attenuation area (< -950 HU) and peak wall attenuation of the fifth generation of the right B10 was 0.484; the coefficient of determination with percentage of low-attenuation area and wall area percentage was 0.40. CONCLUSION. Peak attenuation of the bronchial wall measured at CT correlates significantly with expiratory airflow obstruction in subjects with chronic obstructive pulmonary disease, particularly in the distal airways. © American Roentgen Ray Society.