Surface area, porosity, pore structure and ability to bind to other substances are very important properties in various applications of porous SiO₂. The properties are largely dependent on SiO₂ structure, which is influenced by its preparation. Porous SiO₂ was prepared by coagulation of solutions of an alkali metal silicate. The influence of temperature and pH on the structure of porous SiO₂ was studied by FTIR. It was found that the siloxane four-membered rings along with the expected six-membered rings occurred as basic structural units in all the prepared materials. An increase in pH leads to a significant decrease in the content of the four-membered rings and a decrease in the Si-OH/Si-O⁻ ratio in the silica network. However, the relative amount of Si-OH groups increases. Temperature has no significant influence on the amount of different structural units.