The residence time distribution (RTD) characteristics of three microreactors containing different passive mixing structures, namely, a three dimensional serpentine structure, a split-and-recombine structure and a staggered herringbone structure, were investigated and compared. An experimental input-response technique was applied which required deconvolution of the measured data by modeling of the RTD. The proposed technique provides useful information on optimized application and operation of microfluidic devices. The serpentine reactor and the split-and-recombine reactor show improvement in RTD behaviour, i.e., narrowing of RTD curves, at Re-numbers > 30 due to effective transversal mixing and therefore reduced axial dispersion. In the case of the staggered herringbone structure, dead volumes could be observed which considerably affect the RTD.