A predictive aerosol deposition model, which has been validated by comparison with experimental data from adult test subjects, is used to study particle deposition patterns within the developing human lung. Here, an age-dependent lung morphology is presented in which the growth of bronchial airway dimensions is described by the measurements of Phalen et al. (1985), and the number and sizes of pulmonary airways are derived from Dunnill (1962). Total tracheobronchial, and pulmonary deposition fractions are calculated for different breathing patterns, from sedentary to maximal activity, and particle sizes, ranging over three orders of magnitude. The influences of human subject age and physical activity levels upon regional aerosol deposition within the developing lung are complex; systematic patterns, however, can be identified which are consistent with the effects of linear airway dimensions and particle flow characteristics upon effective particle deposition mechanisms.