This research into the mechanical properties of granite rocks focuses on their porosity and deformability. The study specifically relates to the planned disposal of radioactive waste. Three granitoid types from the Variscan Bohemian Massif of Central Europe have been tested. The investigation boreholes reached depths of up to 100 meters. The porosity was obtained by weighing saturated and dry samples, with saturation provided by water immersion in a vacuum. Young's modulus and Poisson's ratio were determined in uniaxial compression. The shear and longitudinal deformation of each sample was measured using a resistive strain gauge fixed directly on the sample. The samples were subjected to five different loads followed by unloading. A constant gradient of vertical stress of 1 MPa.s⁻¹ was applied during the loading. P-wave and S-wave velocities were measured in three perpendicular directions. The apparatus consisted of four piezoelectric sensors, an ultrasonic pulsar, receivers, and a digital oscilloscope recorder. The frequency was 1MHz. Velocities were measured on naturally wet, saturated, and dried samples. Dynamic elastic modulus was calculated from the measured data. The static Young's modulus varied between 30–60 GPa, while the dynamic modulus rose to 90 GPa. The porosity of the samples varied from 0.6 to 1.4 %. P-wave velocities ranged from 4.4 to 6.9 km.s⁻¹, while S-wave velocities ranged from 2.8 to 3.7 m.s⁻¹. Both P-wave and S-wave velocities generally increase with depth in the borehole. Slight anisotropy was observed in several samples.