[en] This paper investigates the ESR spectra of solutions of acetone and methyl ethyl ketone (MEK) in CFCl₃ (Freon II) that were gamma-irradiated at -196 C. The ketones used in this work were chemically pure. An analysis of the spectra indicated that a reduction of the acetone concentration brings about a decrease in the relative yield of acetonyl radicals and an increase (symbatic) in the yield of cation radicals Me₂CO⁺, the total concentration of radicals being constant over a broad range of acetone concentrations. A reduction of the MEK concentration from 0.5 to 0.08 M lowers the yield of the CH₃COCHCH₃ radicals, with an equivalent increase in the yield of cation radicals