The subject of this paper is usage of CO2 as a working fluid in reversed cycles, and in accordance with that this paper will analyze them. Special attention is given to the CO2 properties, and to its advantages and disadvantages. Paper is based on the existing CO2 systems for cooling supermarkets, as well as heat pumps with special reference to their effectiveness. One of the most important components of the circular process in the refrigeration devices is heat exchanger, in which, by means of the heat from environment, the working fluids are evaporated, which allows to achieve desired temperature. There is no ideal working fluid that would at the same time satisfy the necessary thermodynamic properties and in the safety sense be acceptable for use, on the other hand its use would not be harmful to the environment. Harmful influence of the conventional working fluids on the environment has awakened interest for working fluids with none or minimal harmful influence on the environment. CO2 is also used in such working fluids, whose usage has good prospects for satisfying ecological and usability properties.