Characteristics of porous structure of silica gel Si-60 (pristine and covered by different amounts of pyrocarbon prepared by pyrolysis of acenaphthene, acetylacetone, and glucose, then heated at 500 degreesC in air or hydrothermally treated (HTT) at 150 or 200 degreesC, and also heated at 500 degreesC) were analyzed by using TEM, H-1 NMR, and adsorption-desorption of nitrogen at 77.35 K. The structural parameters were estimated by the direct minimization method or the overall isotherm approximation with a regularization procedure. Pyrolysis of different organics on Si-60 is accompanied by marked changes in the pore structure depending on the nature of precursors. Hydrothermal treatment of silica gel and carbosils at 150-200 degreesC for 6 h results in a strong modification of both pores and outer surfaces of silica gel particles in contrast to heating of pristine Si-60 or carbosils (after HTT) at 500 degreesC in air for 24 h. Computations of the distributions of the pore size and nitrogen adsorption energy, as well as 1H NMR spectra of the interfacial water, reveal an increase in the adsorbent nonuniformity due to hydrothermal treatment, but heating of silica gel and pyrocarbon/silica in air gives the opposite result.