This paper describes the study of molecular hydrogen production from ethanol decomposition by argon microwave TIAGO discharge in air ambiance at atmospheric pressure. In order to estimate the influence of the experimental conditions on the hydrogen production, a wide range of Ar flows, input powers and ethanol flows were tested. The simultaneous use of emission spectroscopy and mass spectrometry techniques allowed us to gain knowledge about the mechanisms which lead to the obtaining of hydrogen and other by-products (C2H2, C(s) ...) at the plasma exit. Results showed a great capability of TIAGO discharges to withstand ethanol introduction as well as an almost complete ethanol decomposition (higher than 99.6%) with high hydrogen selectivity; argon and ethanol flows were found to be the key parameters in the by-products formation. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.