The aim of the research was to evaluate the effect of seed conditioning and flakes steaming (hydrothermal processes) on destruction of cell structure being responsible for seed's mechanical resistance. Commercial rapeseeds were pretreated in different conditions. Seeds of the series A were conditioned at 40°C, flaked and then roasted for 35 min to 94°C. Seeds of the series В were heated up to 80°C, cooled to 49°C, flaked and roasted for 40 min to 97°C. The technological usability and mechanical resistance of control and conditioned seeds were good. The conditioning parameters affected slightly the structure of the series В seeds, only. Distinct changes in the microstructure and particle size of roasted flakes were observed, whereas the microstructure and size of press- -cake particles for both series of seeds were the same. Taking into consideration the requirements for pressing, pretreatment conditions of the series В resulted in more advantageous mechanical properties of flakes.