The mitigation of NOx family of pollutants is a global concern as it has been related to acid rain, ozone layer depletion, breeding health disorder among many others. One of most promising and innovative alternative to the existing conventional abatement technologies is the use of non-thermal plasma reactors. This technology potential includes, for example, being energy efficient, tailoring to many contaminants, scalable for different applications, treating multiple pollutants simultaneously to name few. In order to advance such technological applications successfully, more understanding of the basic and fundamental aspects is needed. For example and although for many years different researchers have been conducted experiments, little has been done to model the effect of electric field variation and the effect geometry or shape of the reactor. In this contribution, the focus has been on the radical production since it is important to control the efficiency of NOx conversion; therefore, key parameters have been identified and can be used as a set of a priori design criteria for an efficient reactor. Graphical illustrations are presented to demonstrate the influence of annulus section, reactor volume and effective electric potential on radical production.