A new method for preparing surface-modified ceramic particles was proposed. Applying a silent mode electrical discharge as the means of activation in the CVD reactions, it is possible to prepare ceramic particles which have organic groups on the surface.<br>The surface-modified ultrafine SiO₂ particles were prepared from various organosilicon compounds. The particles were characterized by thermal analyses and infrared spectrum measurements. The organic groups which were contained in the material existed on the particle surface and hence showed a hydrophobic character. Ultrafine hydrophobic SiO₂ particles could be synthesized directly from the reactant gases without secondary surface-treatment. The surface methyl groups were very heat-stable in comparison with other organic groups.