Dosimetry models for gases mainly have been used to predict absorption in adult humans and laboratory animals. The lack of lower respiratory tract (LRT) lung models for children has discouraged the application of theoretical gaseous dosimetry to this important sub-population. To fill this gap the authors have used several sources of data on age dependent LRT volumes, age dependent airway dimensions, a model of an adult tracheobronchial region, and a model of the adult acinus to construct theoretical LRT lung models for humans from birth to adult. An ozone (O3) dosimetry model was then used to estimate the regional and local uptake of O3 in the (theoretical) LRTs of children and adults. For sedentary breathing, the LRT distribution of absorbed O3, the percent uptake (76 to 85%), and the centriacinar O3 tissue dose are not very sensitive to age. For maximal work during exercise, predicted uptakes range from 83 to 91%, and the regional percent uptakes are more dependent on age than during quiet breathing. In general, total O3 absorption per minute increases with age. Regardless of age and state of breathing, the largest tissue dose of O3 is predicted to occur in the centriacinar region, where many animal studies show the maximal morphological damage due to O3.