In this paper, two new CO2 cascade refrigeration cycles are proposed and analyzed. In both these cycles the top cycle is an ejector-expansion transcritical cycle and the bottom cycle is a sub-critical CO2 cycle. In one of these proposed cycles the waste heat from the gas cooler is utilized to drive a supercritical CO2 power cycle making the plant a combination of three cycles. Using the first and second laws of thermodynamics, theoretical analyses on the performance characteristics of the cycles are carried out. Also a parametric study is conducted to optimize the performance of each cycle under various operating conditions. The proposed cycles exhibit a reasonable value of COP (coefficient of performance) with a much less value of compressor discharge temperature, compared to the conventional cycles. (C) 2011 Elsevier Ltd. All rights reserved.