Selective catalytic reduction of NOx by NH3 (NH3-SCR) over V2O5/TiO2-based catalysts is recently reported to be an anthropogenic emitter of N2O that is a global warming gas with a global warming potential of 310. Therefore, this review will get a touch on significance of some parameters regarding N2O formation in the deNOxing reaction for fossil fuels-fired power plants applications. The N2O production in NH3-SCR reaction with such catalysts occurs via side reactions between NOx and NH3 in addition to NH3 oxidation, and the extent of these undesired reactions depends strongly on the loadings of V2O5 as a primary active component and the promoter as a secondary one (WO3 and MoO3) in the SCR catalysts, the feed and operating variables such as reaction temperature, NO2/NOx ratio, oxygen concentration, gas hourly space velocity, water content and thermal excursion, and the physical and chemical histories of the catalysts on site. Although all these parameters are associated with the N2O formation in deNOxing reaction, details of some of them have been discussed and a better way of suppressing the N2O production in commercial SCR plants has been proposed.