This paper reports a numerical study of the mass transfer characteristics during Taylor flow in mini/microchannel reactors. A finite-element implementation of the phase field method was used to predict the hydrodynamics of the two-phase flow. The phase distribution thus obtained was used to define the computational domain to model the reactive mass transfer. The reaction system of the absorption of CO2 into aqueous NaOH solution was considered. Channels with characteristic dimensions ranging from 100 mu m to 750 mu m were modeled with cross-flow and flow-focusing inlet configurations. The effect of channel length was studied by varying the residence time in the transient simulation. The results indicated that channels having a small characteristic dimension could yield reductions in the residence time, and therefore the reactor size, by as much as 85%. This reduction was further enhanced by higher concentration levels of the liquid reactant and increased temperatures. The inlet mixing region was found to have a significant influence on the total mass transfer. The channel wall wettability was found to affect the mass transfer characteristics negligibly. The predictions from the currently proposed model were compared with available experimental data, as well as with predictions of an earlier unit cell-based model, and a good agreement was obtained. (C) 2013 Elsevier Ltd. All rights reserved.