In this paper, various titanium dioxide (TiO2) ceramic properties (density, microstructure and electrical resistance) were investigated after thermal treatment in air and under high vacuum conditions. In the present research, cylindrical-shaped samples were used, which were obtained from the plastic TiO2 ceramic mass by extrusion method. When the temperature of thermal treatment in the air is increased from 1100 to 1350 °C, sintering degree, ceramic density and grain size also increase, while porosity decreases. The density of the obtained ceramic samples reaches 82% of the theoretically possible. It has been found that during the process of sintering mainly open porosity decreases. Thermal treatment in air influences electrical resistivity of titanium dioxide ceramic samples; after thermal treatment under high vacuum conditions electrical resistivity of samples significantly decreases, and it has been observed that the samples with the highest density and the biggest grains have the lowest electrical resistivity.