An air conditioning system including an outdoor heat-exchanging unit, at least one indoor heat-exchanging unit, a gaseous refrigerant line connected between the outdoor heat-exchanging unit and the indoor heat-exchanging unit, to allow a refrigerant in a gaseous state to flow between the outdoor heat-exchanging unit and the indoor heat-exchanging unit, and a pressure compensation device for increasing a pressure of the gaseous refrigerant flowing through the gaseous refrigerant line. The pressure compensation device is located along the gaseous refrigerant line at a position closer to the indoor heat-exchanging unit than to the outdoor heat-exchanging unit. A pressure compensation device for use in an air conditioning system is also provided.