This paper studies the influence of three volute geometries of a single-stage centrifugal compressor, using the same vaned diffuser and impeller, the only differences are given by the volute geometry: cross section area and volute tongue. The objective of this research is to determine which of parameters has a major impact on the compressor and how much are the operating range and overall performance influenced. This study is based on numerical aerodynamical simulation at 15000rot/min, which is the design speed of the compressor. The numerical results show that the volute tongue has a major impact on the overall performance of the compressor.