Ground and second excited electronic states of halogen and monomethyl substituted vinoxy radicals were studied by multireference configuration interaction (MRCI) calculation. Optimized geometries, rotational constants and vibrational frequencies of vinoxy and 1-fluorovinoxy showed good agreement with experimental values. Differences in calculated and observed (B) over tilde-(X) over tilde electronic transition energies were less than 0.1 eV and observed trends of blue shift upon increasing the number of substituted halogen atoms were reproduced by MRCI calculation. Observed fluorescence lifetimes of the vibrationless level in (B) over tilde state were in good agreement with calculated values. Rotational profiles of the 0-0 vibronic bands were successfully simulated with calculated rotational constants and transition dipole moments. Energy differences between planar and nonplanar optimized geometries in (B) over tilde state showed good correlation with the onset of fast nonradiative decay in (B) over tilde state, supporting the proposed mechanism of nonradiative decay via avoided crossings from (B) over tilde to (A) over tilde state which is followed by the decay to the ground state via conical intersections.