In ethylene-derived diradicals, there are four closely lying electronic states differing by the occupations of oxygen's p-orbitals. The lowest singlet state is multi-configurational and the weights of different configurations depend on the geometry. While its diradical structure was described long time ago, 2 the exact shape and orientation of orbitals can be established only by accurate correlated calculations. The NTO analysis using SF wavefunctions confirms openshell nature of the singlet states and serves as a basis for the extension of El-Sayed's rules. The lowest triplet state features a very shallow PES profile along the torsional coordinate, with a low-energy (∼1 kcal/mol) MECP located close to the equilibrium triplet structure. There is no stable minima corresponding to the singlet diradical.