The stability of the footwear napa on flexion is an important property associated with the structure of leather tissue and the finishing films on upper side (front side) of leather. Stability of the smooth upper side footwear napa refers to the stability of the dyestuff and the thin layered polymeric structures of the upper side of leather build during the final technological process. In the experimental part, flexion resistance was tested on two samples of footwear napa, differently tanned and finished: footwear napa dyed crust and footwear napa corrected upper side of leather. The test results showed differences in flexion strength and better flexion strength of footwear napa corrected upper side of leather. Test samples of the footwear napa were subjected to thermogravimetric analysis (TGA) for their heat resistance and evolved gases (TG-IR) monitoring during decomposition, with the purpose of linking differences in the content and structure of tannins and finishing additives with their print in nature.