In this work, an investigation of SiOx nanopowders synthesised by the laser ablation of crystalline silicon in water, evaporation of solvent and heat treatment is presented. The material is obtained for the first time by laser ablation in large quantities, which allows the use of a variety of physicochemical methods. The chemical composition and structure of the nanopowders were analysed before and after calcination in air and/or argon from 200 to 1000 °C. The particles prepared by laser ablation of a silicon target in water contain an amorphous and/or crystalline silicon core and a silicon oxide shell. Calcination results in the disappearance of crystalline silicon reflections in diffraction patterns and the appearance of oxygen vacancies in the silica. These materials are potentially important for such applications as optics, sensors and catalysis.