This document discusses how intersubject variability in extrathoracic airway geometry affects particle deposition. It finds that larger values of the shape factor and smaller minimum cross-sectional areas in the nasal airways lead to higher deposition there, due to increased turbulence. Similarly in the oral airways, smaller equivalent diameters cause higher deposition. The results show deposition efficiency approaches 100% at very low and high flow rates in both nasal and oral airways. Intersubject variability most affects penetration efficiency and downstream deposition of ultrafine particles.