Adsorption of acetone on an SiO₂ (aerosil) surface at 300 and 77 K was studied by IR spectroscopy. It was shown that, given a small surface coverage, the carbonyl group interacts simultaneously with two OH groups (ν_OH = 3420 cm^-1, ν_C=O = 1696 cm^-1) and, at a higher adsorbed amount of acetone, predominantly with one OH group; in this case, the maximum of the absorption band of OH is additionally shifted toward lower frequencies (ν_OH = 3280 cm^-1), and the disturbance of the carbonyl group decreases (ν_C=O = 1708 cm^-1). It was established that the adsorption on isolated silanol groups of the methoxylated surface results in 1:1 complexes irrespective of surface coverage.