This paper presents a comprehensive 3D numerical simulation of reacting flows in micro scale dimension through centrifugal, or Lab-On-a-CD (LOCD), and pressure-driven, or Lab-On-a-Chip (LOC) devices. Three different serpentine channel configurations (rectangular, triangular and sinusoidal) are investigated. In these configurations, two chemical species enter from two inlets and according to an irreversible chemical reaction, start yielding other species. Both Newtonian and generalized Newtonian fluids are considered in the simulations and the results are compared for both LOC and LOCD devices. Besides, the effects of different parameters such as the aspect ratio of channels’ cross section, inlet flow rate, angle of fabrication in LOCD devices and the radial distance are also investigated. It is found that the products are generated in the vicinity of the LOCD microchannel corners, but in LOC devices, reactants yield their product on the top and bottom walls of the microchannel. The best fabrication angle depends on the configuration of the microchannels and the rectangular configuration has the maximum production factor for AR = 1. Besides, secondary vortices for Newtonian and generalized Newtonian fluids in the LOC and LOCD devices are compared in detail. © 2017 Elsevier B.V.