Isotropic hyperfine parameters of a set of iminoxy radicals are investigated using hybrid density functional and quadratic configuration interaction methods. The systems studied are R1R2C=NO radicals, where R-1=H, BH2, CH3, NH2, OH, F, AIH(2), SiH3, PH2, SH, Cl and R-2=H. Theoretical results indicate that magnitude of the hyperfine coupling with iminoxy C-13 nucleus due to the particular isomer of the radical is strongly affected by electronegativity of the substituents R-1 and R-2. A(iso)(C-13) varies from 6.7 to 56.2 G for Z (and from 45.6 to 18.7 G for E) isomers of the iminoxyls depending on the substituent (AIH2 and F, respectively).