Modern aeroengines strive for greater efficiency and safety. With ever increasing by-pass ratios and therefore overall pressure ratios in the compressor, the stall margins of the last stages in high pressure compressors shrink, as tip gap ratios increase. A potential remedy for the low stability of these compressor stages are casing treatments. Essentially grooves in the casing of the compressor, they aim to impede the tip vortex and other secondary flow phenomena to delay the onset of a tip stall of the rotor. In this research work the rules of thumb by Kau et al. as well as the findings by Nezym were utilised to create three circumferential groove casing treatments: one with an equal groove depth and two others with grooves which become shallower towards the end. These were subsequently tested in a rear stage of a high-pressure subsonic compressor using ANSYS CFX. Although the performance of the casing treatments themselves was lacklustre, an interesting phenomenon was observed; for all casing treatments the mass flow drops temporarily, when the compressor was throttled, before recovering again. In conclusion further analysis would be necessary to confirm the suspicion of a rotating part-span stall cell near the front tip of the rotor. However, the results did highlight the necessity for a more stringent definition of the rules for the creation of circumferential groove casing treatments, especially when also manipulating the groove depth.