This paper considers carbon dioxide transcritical and supercritical power cycles driven by low temperature flue gases exhaust from a gas turbine. Transcritical CO2 Rankine and supercritical CO2 Brayton cycles were studied at steady state conditions and their performance were compared. Furthermore, the study carried out parametric analysis to investigate the cycles' performance in terms of thermal efficiency and the network output at different turbine inlet temperatures. A mathematical model was developed to carry out the analysis based on the first law of thermodynamics. In order to simulate cycle performance and generate parametric tables a simulation model was developed using Engineering Equations Solver (EES). The efficiencies of the cycles were compared and it was found that transcritical Rankine cycle generates higher efficiency and net power output compared to supercritical Braytoncycle for the same turbine inlet conditions. Parametric analysis showed that as the turbine inlet temperature increases, the gas heater pressure that gives optimum efficiency increases. © 2006-2015 Asian Research Publishing Network (ARPN).