A diffuse interest on cycle modifications for R744 applications that allow to achieve better CO2 cycles performance can be inferred from the literature. The parallel compression cycle in flash tank configuration seems to be an interesting solution and the authors conducted an experimental campaign to estimate the critical parameters that influence its performance in an actual cycle. Previous to that a thermodynamic analysis was lead to investigate the expectable performance of the cycle and the influence of key parameters such as compressors volumetric flow ratio and separator efficiency. The thermodynamic model designed also allowed the definition of the limit conditions for an optimal operability of the cycle of interest. The experiments showed that the theoretically reachable improvements in terms of refrigerating capacity and coefficient of performance are threatened by several phenomena which may occur in a real system. These detrimental effects are described and commented in the paper. The paper also includes experimental data obtained during the experimental activity for operating conditions typical of commercial refrigeration applications.