The aim of the research is to classify and evaluate the size of deformations appearing during milling of thin-walled elements representing a pocket form made of aluminum alloy AW-7075A. Finishing, which is the purpose of the research, was carried out at the full depth of cut ap = 15 mm, milling the entire height of the wall in one pass. Deformations during machining were correlated with the geometric accuracy of the workpieces after machining. During the tests, deformations were measured with a laser displacement sensor, and the temperature of the samples was measured using a resistance temperature sensor. The tests made it possible to identify deformations occurring during the milling of thin-walled elements. The course of deformation during milling was analyzed, from which the value of deformation caused by milling, the reaction to this deformation and its time were extracted, additionally, permanent distortion of the workpiece was detected. The results show the effect of the ratio of the height to the thickness of the thin-walled element on its geometric accuracy after machining in the form of straightness and flatness of the samples. The test results were compared to the tests carried out on the Ti6Al4V titanium alloy, which confirmed the influence of the material selection on the course of deformations during milling.