The optimization of microreactor designs for applications in chemical process engineering usually requires knowledge of the residence time distribution (RTD). The applicability of established models to microstructured reactors is currently under debate [1-4]. This work presents investigations of the RTD behaviour for gas flows in microstructured devices by CFD (computational fluid dynamics) simulations and new experimental data for the RTD of different microstructured reactors (some provided by industrial partners). Influence of the in- and outlet regions of the devices and uneven flow distribution inside the microstructure on the RTD are discussed. Hereby, boundary conditions for the applicability of commonly used dispersion model and the correlation proposed by Taylor and Aris for the model parameter Bodenstein number Bo are explained. The experimental data for the RTD of the microreactors investigated are analysed, whereby a good agreement of simplified models for the RTD of the complete devices (including- in and outlet regions) is found. The determination of the model parameter may be difficult as several factors have to be considered. Here, an extended correlation based on experimental data is suggested. (C) 2012 Elsevier B.V. All rights reserved.