position α to the radical centre are formed on oxidation of 4H-imidazole mono- and di-N-oxides in ethanolic solutions of NH3 and CH3NH2. α-Fluorinated imidazolidine nitroxides have been obtained from 3-imidazoline-3-oxide derivatives by treatment with XeF2 in CH2Cl2. Nucleophilicsubstitution of the fluorine atom resulted in formation of aminoimidazolidine nitroxides.