The porosity of polysiloxane microspheres obtained by emulsion processing of variably modified polyhydromethylsiloxane (PHMS) and subjected to pyrolysis in an Ar atmosphere at 450–650°C was studied. Materials having micro- and mesopores with specific surface areas (SSAs) of up to 786m2/g and pore volumes of up to 0.35cm3/g were obtained. A high porosity was displayed by the microspheres heated at 600°C that underwent deep depolymerization processes. Some polysiloxane microspheres were ceramized at temperatures of 1200–1500°C and were subjected to etching by 35% aqueous HF. The microspheres heated to 1200–1400°C were free of microcracks, whereas those ceramized at 1500°C showed microcracks and macropores, although they preserved their spherical structure well. All of the microspheres ceramized at temperatures of 1200–1400°C had low porosity. HF etching granted high micro- and mesoporosity to the materials ceramized at 1300–1500°C. Microspheres heated at 1500°C showed specific surface areas above 1000m2/g after etching. These microspheres had low oxygen contents and were mostly composed of silicon carbide. Since they also showed macroporosity, HF etching of the polysiloxane microspheres ceramized at 1500°C could be used to obtain hierarchically mesoporous-macroporous ceramic microspheres.