The diploma thesis deals with "flexibility properties of thermally modified structural timber" and especially the evaluation of its qualitative parameters in the area of mechanical attributes.Obtaining a dynamic module of elasticity by a non-destructive measurement test, comparison with modules obtained by a static test according to a valid standard and finding their mutual correlations.Determination of the correlation between the modulus of elasticity and the density of thermally modified structural timber. At the end of the diploma thesis the results are published, including a comment on the results and outcome for the practice.