Using computed tomography (CT), the authors determined significant signs of overinflation. Both the pulmonary function tests (PFT) and CT of 74 patients who underwent thoracic surgery for lung cancer (44 with normal lung function, 30 with chronic obstructive pulmonary disease) were reviewed. The following were correlated with forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC): tracheal index (transverse/anteroposterior diameter), sterno-aortic distance, thoracic cage ratios (anteroposterior/transverse diameters) at the tracheal carina (TC1) and 5 cm below (TC2); and depth of the azygoesophageal recess and the presence of intercostal lung bulging (ILB). Significant correlations were observed between FEV1/FVC and tracheal index (r = 0.578, p < 0.0001), TC1 (r = -0.523, p < 0.0001), TC2 (r = -0.533, p < 0.0001), and ILB (r = -0.462, p < 0.0001). Correlations were significant but weak between FEV1/FVC and sterno-aortic distance (r = -0.351, p = 0.0027) and depth of the azygoesophageal recess (r = -0.308, p = 0.0085). Reduced tracheal index and increased anteroposterior diameter of the thoracic cage correlated most significantly with a pulmonary function index of chronic airway obstruction.