Geometries of imidoyl radicals Y-C(.)=NMe have been determined by means of ab initio UHF/VTZP calculations. The local radical structure is found to be essentially indipendent of the electronic nature of the alpha-substituent, the angle YCN bond angle being about 128 degrees. This structural information is in contrast to that obtained from the magnitude of the experimental isotropic C-13 hyperfine splitting (hfs) constants indicating that imidoyls bearing electropositive alpha-substituents such as silyl groups are nearly linear about C-alpha. UQCISD/VTZP calculations on H3Si-C()=NH confirm that alpha-silylimidoyl radicals should be largely bent at Ca-alpha. At variance with what was previously found in other localized radicals, UMP2/DZP/UHF/VTZP calculations do not closely reproduce the hfs constants at the radical center but underestimate largely their values owing not only to slow convergence of the doubles amplitudes in Moller-Plesset perturbation theory but mainly to neglect of single excitations. Excellent agreement with experiment has been achieved at the UQCISD/DZP//UHF/VTZP level.