Microchannel technology has attracted great interest due to its potential for process intensification and design of compact devices. In this study, isothermal gas-liquid flow patterns (Taylor and stratified) developed in a rectangular microchannel were numerically evaluated through the volume of fluid (VOF) model. Hydrophilic (theta(w)=25 degrees) and hydrophobic (theta(w)=105 degrees) microchannels were investigated. The numerical results were compared with experimental data. A comparison between numerical and experimental data and some available correlations showed good agreement. At similar feeding conditions, the model was able to capture the different gas-liquid flow patterns expected when the wall contact angle is varied. Thus, this work elucidated the use of CFD for the evaluation of the impact of variations of the wall wettability on isothermal gas-liquid flow patterns developed in microchannels. This procedure can be used as a source of preliminary information on the flow morphology expected in microfluidic devices subjected to superficial treatment. (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.