The paper aimed to examine if the mechanical characteristics (tensile strength, elongation, and friction) of the selected flexible packaging materials (BOPP and PET/PE) change after the packaging process. Some researchers have shown that mechanical characteristics can change because of the various effects to which foils are exposed (temperature, transport devices, solvents, etc.). The measurement of tensile strength and elongation was carried out according to SRPS G.S2.734, and the measurement of friction according to ASTM D 1894. The results show that there were no significant changes in the examined mechanical characteristics that could affect the functionality of the packaging.