Computational fluid and gas dynamics methods are used at all stages of design, including blade machine design: from the creation of a schematic design to a detailed study of all the main units [1, 2]. The industries using refrigeration centrifugal compressors (oil refining, chemical, food) development requires the machines unit capacity, efficiency and reliability increase, the weight and size characteristics and metal consumption decrease. Since this machine type production often has a small-scale or individual character, and the needs for machine specified characteristics maintain during the entire service life exists, design remains an important stage in the creation process. This article is devoted to the possibility of validating the calculations using the numerical gas dynamics methods research. The centrifugal compressor end stage numerical and a full-scale research were made during the investigation; refrigeration centrifugal compressor end stage full-scale investigation carried out by D.A. Kapelkin was chosen as a base of the research [3]. As a result, the diffuser flow numerical simulation results were analyzed and the calculated and full-scale characteristics comparison was carried out. Recommendations for the numerical gas dynamics methods application are given in a particular case, applied to refrigeration centrifugal compressors vane diffusers gas-dynamic calculations.