Carbon nanotube is being considered as a prospective alternative for the existing Silicon technology in present days. The advancement of Silicon technology, at present, has slowed down considerably because of its various material issues and scaling limitations and so, carbon nanotubes have gained the attention of researchers around the world over. In this literature, the effect of change of dielectric constant of the gate material on the performance of carbon nanotube field effect transistor (CNTFET) with non-ballistic conduction is extensively investigated. It is found in this study that with the value of dielectric constant of the gate material greatly improves the current output of CNTFET considering Non-Ballistic conduction. In addition to this, the obtained results are compared with previously reported CNTFET with ballistic conduction data for a better perception of the non-ballistic conduction with effects. Also, the on and off state current ratios have been calculated and plotted in this work to further contrast the ballistic and non-ballistic conduction of CNTFET.