Diploma thesis is focused on evaluation the influence of chemical-thermal modifications of beech wood on its biological resistance and physical-mechanical properties. Theoretical processing of issues is concern the chemical and thermal modification of wood and their technological processes, applications and not least properties of thermal and chemical modified wood. The practical part describes experimental verification effects of thermal modification combination with paraffin wax, namely testing the resistance of modified wood against moulds (Aspergillus niger) and wood decay fungi (Poria placenta and Trametes versicolor). Physical properties such as water sorption, swelling and weight percent gain (WPG) were also examinated. Between measured mechanical properties of beech wood were included Charpy impact test and Brinell hardness.