The performance of the transcritical CO2 systems, when used only for cooling applications at high ambient temperatures, is substantially low. The subcooling of the gas after the gas cooler in such systems, by either integrated or dedicated types of cooling, is proven to be beneficial. In the present study, the performance enhancement by using two methods of the former (integrated) type, namely an integrated vapour absorption refrigeration system (VARS) and expander-compressor unit (ECU) is investigated. The former utilises the waste heat available in the discharged gas downstream of the compressor in the transcritical CO2 system to operate a LiBr-H2O VARS. Three different configurations of the absorption system are considered, namely, single effect (SE), series double effect (DE), and series double effect with dual heat input (DEDH). The average COP improvement of the CO2 system is found to be 29 and 27 % using SE and DEDH systems respectively. The latter (ECU) utilises the work done by the expander to operate the compressor to compress a part of the gas back to the gas cooler pressure while subcooling the main gas stream. Results show enhancements in COP up to 33 % compared to the simple system. Therefore, any of the above subcooling methods can be used for performance enhancement of the transcritical CO2 refrigeration systems at high ambient temperatures.