Iminoxy radicals (R1R2C=N-0(center dot)) possess an inherent ability to exist as E and Z isomers. Although isotropic hyperfine couplings for the species with R-1 = H allow one to distinguish between E and Z unequivocal assignment of the parameters observed in the EPR spectra of the radicals without the hydrogen atom at the azomethine carbon to the right isomer is not a simple task. The iminoxyl derived from o-fluoroacetophenone oxime (R-1 = CH3 and R-2 = o-FC6H5) appears to be a case in point. Moreover for its two isomers the rotation of the o-FC6H5 group brings into existence the syn and anti conformers depending on the mutual orientation of the F atom and C=N-O-center dot group making a description of hyperfine couplings to structure even more challenging. To accomplish this a vast array of theoretical methods (DFT OO-SCS-MP2 QCISD) was used to calculate the isotropic hyperfine couplings. The comparison between experimental and theoretical values revealed that the E isomer is the dominant radical form for which a fast interconversion between anti and syn conformers is expected. In addition the origin of the significant A(F) increase with solvent polarity was analyzed.