This work is dedicated to the mixing characterization inside two geometries of minireactor by using an electrochemical method. The first one is composed of only minichannels crossing at right angles while the second one includes crossing minichannels and T-shaped parts. The used method consists to measure the limiting diffusion current at the surface of microelectrodes flush-mounted into the wall at the 10 minichannels outlet of each network. The limiting diffusion current is linked to the concentration of an electroactive species flowing in the minichannels and its measurement allows the characterization at the cell outlet of the radial dispersion by using an electrochemical tracer method. The electrochemical tracer is injected in the middle of the upstream part of the cell and the cell mixing effectiveness is characterized for Reynolds number ranging between 55 and 250 by comparing the tracer response on the microprobes located at each outlet channel. The experimental results show distinctly that the second geometry is more promising in terms of mixing process than the network of crossing minichannels. Pressure drop measurements are carried out inside the two geometries at Reynolds numbers ranging from I to 1000 in order to evaluate the energetic dissipation. The data show, for both cells, that the pressure loss can be represented by a Reynolds-Forchheimer-type equation characteristic of porous media. (c) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.