To determine the characteristics of the elderly in high - resolution computed tomography (HRCT) lung densitometry, mean lung density (MLD) and relative area of the lungs showing attenuation values less than -950 HU (RA(950)) on HRCT were evaluated in nonsmoking control subjects (n = 80) and patients with asthma (n = 80) in relation to their age and pulmonary function. MLD was significantly decreased, and RAW was significantly increased with increasing age in both asthmatics and controls. The MLD values were significantly lower in asthmatics compared with controls in subjects aged between 60 and 69 years and over age 70. RAgsov alues were significantly higher in asthmatics compared with controls in subjects aged between 50 and 59 years, between 60 and 69, and over 70. % FEV(1) and FEV(1) / FVC were significantly decreased in elderly asthmatic patients over 70 years of age compared with the values in those under 49. Percent residual volume (% RV) was significantly larger in patients over 70 years of age than in those between 50 and 59, and under 49 years. RAW was significantly larger in patients with steroid-dependent intractable asthma (SDIA) between 50 and 59 years of age, and between 60 and 69 compared with RA 950 in those without SDIA. However, RAW did not differ significantly between SDIA and non-SDIA in patients over age 70. The results suggested that in % LAA of the lungs on HRCT was significantly increased in the elderly subjects with and without asthma, and it was significantly higher in the elderly asthmatics than the elderly controls.