The purpose of our study was to assess the normal range of CT measures of emphysema and air trapping in young men with normal lung function.A cohort of 70 young men with high-normal spirometry and body plethysmography underwent paired inspiratory and expiratory CT. Visual and quantitative scores of emphysema and air trapping were obtained. On CT, emphysema was defined as the 15th percentile of the attenuation curve (Perc(15)), and as the percentage of inspiratory voxels below -950 (IN(-950)) and below -960 (IN(-960)) HU. On CT, air trapping was defined as the expiratory-to-inspiratory ratio of mean lung density (EI-ratio(MLD)), and the percentage of voxels below -856 HU in expiration (EXP(-856)). Means, medians, and upper limits of normal (ULN) are presented for the total population and for smokers and nonsmokers separately.The mean age (A-A?A 1/2 SD) of the subjects was 36.1 A-A?A 1/2 9.3 years. Smoking history was limited (range, 0-11 pack-years). Spirometry was high normal, ranging from 113\% to 160\% of predicted for vital capacity (VC), and from 104\% to 140\% of predicted for forced expiratory volume in 1 second (FEV(1)). The ULN was 2.73\% for IN(-950), 0.87\% for IN(-960), -936 HU for Perc(15), 89.0\% for EI-ratio(MLD), and 17.2\% for EXP(-856).Visual CT scores showed minimal emphysema in eight (11\%), > 5 lobules of air trapping in five (7\%), and segmental air trapping in three (4\%) subjects. CT measures were similar for never- and ever-smokers.We report the normal range of CT values for young male subjects with normal lung function, which is important to define pulmonary disease.