Electron paramagnetic resonance (EPR) spectroscopy was applied to study paramagnetic species stabilized in Na-A zeolite exposed to gaseous methane and gamma-irradiated at 77 K. Two types of EPR spectra were recorded during thermal annealing of zeolite up to room temperature. Owing to the results for the zeolite exposed to (CH4)-C-13 the multiplet observed at 110 K was assigned to a (CH3Na+)-C-.-Na-... complex. After decay of the multiplet, the isotropic quartet of methyl radical was recorded in the temperature range of 170-280 K. On the basis of the EPR parameters it is postulated that (CH3)-C-. radicals in this temperature region are able to freely rotate inside the zeolite cage. The structures of the (CH3...)-C-. Na+ adsorption complex and respective hyperfine coupling constants were calculated by applying DFT quantum chemical methods. Two different models were applied to represent the zeolite framework: the 6T structure of one six-membered ring and the 3T cluster. The hyperfine coupling constants calculated for the (.)CH3(...)Na(+) adsorption complex for both applied models show very good agreement with those obtained experimentally.