The typical features of a summer smog episode in the highly complex terrain of the Province of Bolzano (Northern Italy) were investigated by numerical modelling with two non-hydrostatic models, ground-based monitoring stations, and vertical profiling with two sodars and an ultra-light aircraft. High ozone concentrations are most likely to appear in situations where the local circulation in the valleys is decoupled from the synoptic flow above during anticyclonic weather regimes. Both models (MM5 and TVM) produced similar results and were able to simulate the local winds in the valleys. A comparison of the measured data to the model simulation results made an evaluation of the performance of the two models in such complex terrain possible. Both models proved to be suitable for the simulation of the meteorological conditions during such summer smog episodes in complex terrain.