Confined Impinging jets Reactors have recently found many interesting applications. Their ability to provide very efficient mixing performances is of paramount importance in the production of very fine particles. In fact, in many particle precipitation processes mixing plays a crucial role in determining the final particle size distribution and therefore the final product quality. Relevant examples are the production of polymeric nano-particles for pharmaceutical applications through solvent displacement, the production of many oxides through sol-gel processes, as well as standard reactive crystallization processes. in order to develop reliable design and scale up rules and in order to understand and master the interaction between mixing and particle formation, it is of crucial importance to resort to modeling and simulation tools. In this work mixing and reaction in these devices is studied with Computational Fluid Dynamics (CFD) by using the Large Eddy Simulation (LES) approach coupled with a subgrid-scale mixing model, to take into account the effect of molecular mixing. The performance of the model is investigated through a sensitivity analysis and eventually predictions are compared with experimental data and with simulations obtained by using the Reynolds-Averaged Navier-Stokes equations (RANS) approach. (C) 2008 Elsevier Ltd. All rights reserved.