The doctorate paper “Improvement of Deciduous Wood Properties by the Thermal Treatment Method” contains investigation of the possibility to obtain a new product from the soft deciduous wood with improved properties and high value added. On the basis of the literature data and tendencies in the thermal modification of wood, I chose the soft wood of the species of local deciduous trees (grey alder, aspen and birch) as an object of research by hydrotermically modifying (HTM) the wood under the pressure in the environment of high amount of water vapour. The task of the doctorate paper is to find the optimal parameters of HTM mode by adjusting them to the external heating autoclave, in order to obtain deciduous wood with the 3rd usage class (in external conditions without a contact with soil), 2nd-1st durability class against decay fungi, decreased amount of humidity in the wood at different contents of the relative humidity in the air, high shape stability and against swelling efficiency, as well as losses of mechanical resistance.