In this study, the deformability of airway walls is taken into account to study airflow patterns and airway wall stresses in the first generations of lower airways in a real lung geometry. The lung geometry is based on CT scans that are obtained from in vivo experiments on humans. A partitioned fluid–structure interaction (FSI) approach, realized within a parallel in-house finite element code, is employed. It is designed for the robust and efficient simulation of the interaction of transient incompressible Newtonian flows and (geometrically) non-linear airway wall behavior. Arbitrary Lagrangian–Eulerian-based stabilized tetrahedral finite elements are used for the fluid and Lagrangian-based 7-parametric mixed/hybrid shell elements are used for the airway walls using unstructured meshes due to the complexity of the geometry. Airflow patterns as well as airway wall stresses in the bronchial tree are studied for a number of different scenarios. Thereby, both models for healthy and diseased lungs are taken into account and both normal breathing and mechanical ventilation scenarios are studied. Copyright © 2008 John Wiley & Sons, Ltd.