Carbon Nanotube Field Effect Transistor (CNTFET) is one of the most promising candidates in the near future for digital design due to its better electrostatics and higher mobility characteristics. Parameters that determine the CNTFET performance are the number of tubes, pitch, diameter and oxide thickness. In this paper, a power gating design methodology to realise low power CNTFET digital circuits even under device parameter changes is presented. Investigation about the effect of different CNTFET parameters on dynamic and standby power is carried out. Simulation results reveal that the power gated circuits suppress a maximum of about 67% dynamic power and 59% standby power compared to conventional circuits.