To determine the relative roles of perfusion, inhalation, and ventilation lung scintigraphy, studies were done respectively in 48, 50, and 34 of 54 primary lung carcinoma patients (prior to thoracotomy and subsequent radical tumor resection). We observed the relationships between both the size of perfusion, inhalation, and ventilation defects observed scintigraphically, and the size of the mass lesion seen radiologically. We also estimated the correlation between those scintigraphic classifications and pTN. Although inhalation and perfusion images exhibited similar patterns, in hilar type lung carcinoma patients, the inhalation study showed superior mass lesion delineation. In peripheral type lung carcinoma, however, the incidence of negative inhalation defect (52%) differed significantly from that of negative perfusion defect (21%) (p less than 0.05). Xe-133 gas ventilation has limitations but is occasionally helpful in detecting obstructive airway disease. The coexistence ratio of COPD in lung carcinoma patients showed no significant difference from that of COPD in the controls. Perfusion and inhalation classification did not correlate with pTN factor.