The NOx selective catalytic reduction (SCR) with ethanol has been investigated over alumina supported silver catalyst with a special attention to the main involved reactions depending on the temperature test. With this aim, the possible reducers from ethanol transformations were also evaluated (C2H5OH, CH3CHO, C2H4, CO). In addition, the contributions of the gas phase reactions and the alumina support were also pointed out. Based on the C-products and N-compounds distributions, it is assumed that at low temperature (T < 300 °C), ethanol reacts firstly with NO + O2 to produce acetaldehyde and N2. For higher temperatures, two reaction pathways have been proposed, supported by the CH3CHO-SCR results: a direct reaction between NO2 and CH3CHO, or via –NCO species.