Atypical radiologic images of pulmonary tuberculosis are common in elderly and in diabetic patients. To investigate the relationship of chest radiographic findings of tuberculosis to age in diabetic and nondiabetic patients, we compared the chest radiographic findings of 192 inpatients with pulmonary tuberculosis and diabetes with those of 130 patients with pulmonary tuberculosis alone. The proportion of patients with lower lung field lesions progressively increased with age (r(S) = 0.89, p < 0.01), whereas the frequency of cavitation steadily decreased with age (r(S) = -0.79, p < 0.05). In diabetic patients, a high frequency of lower lung lesions and cavitation was observed in all age groups. We speculated that, in older patients and in diabetics, the increased alveolar oxygen pressure in the lower lobes favors development of lower lobe disease in these groups.