Velocity profiles, local deposition efficiencies (DE), and deposition patterns of aerosol particles in the first three generations (i.e., double bifurcations) of an airway model have been simulated numerically, in which the airway model was constructed from computed tomography (CT) scan data of real human tracheobronchial airways. Three steady inhalation conditions, 15, 30, and 60 L/min, were simulated and a range of micrometer particle sizes (1-20 mum diameter) were injected into the model. Results were then compared with experimental and other numerical results which had employed either similar model geometry or test conditions. The effects of inhalation conditions on velocity profiles and particle deposition were studied. The data indicated that the local deposition efficiencies in the first bifurcation increased with a rise in the Stokes number (St) within St range from 0.0004 to 0.7. Within the same St range, DE in the second bifurcations (both left and right) was dropped dramatically after St increased to 0.17. Also, the second bifurcation in the right side (B2.1, closer to first bifurcation than left side, B2.2) was found to show a much higher (almost double) DE than the left side. This may be due to the fact that the left main bronchus is longer and has greater angulation than the right main bronchus. Generally, the present simulation using a computational fluid dynamic (CFD) technique obtained concurrent results with subtle differences compared to other works. However, due to omission of larynx in the model, which is known to significantly modify airflow and hence particle deposition, the present model may only serve as the "stepping stone" to simulating and analyzing dose-response or inhalation risk assessment visually for clinical researchers.