CT scans of 474 patients with suspected chronic obstructive pulmonary disease (COPD) were retrospectively evaluated by automated software. There was a correlation between the total lung capacity (TLC) and the total lung volume (TLV) (r=.675, P<.001), between the TLC and the total emphysema volume (r=.571, P<.001), as well as between the TLC and the emphysema index (r=.532, P<.001), respectively. The correlation between the TLC and the TLV was dependent on the COPD severity according to the Global Initiative for Chronic Obstructive Lung Disease classification (chi(2)=6.3079, P=.043). The TLC allows a prediction of clinical illness severity.