Hadronic electric dipole moment experiments (EDM) probe CP-violating phases from New Physics and also from the so-called theta_QCD with highest sensitivity than any other EDM experiments. Storage ring EDM methods provide a new opportunity in terms of improving the statistical and systematic errors in the quest of a more sensitive EDM probe. The all-electric and the hybrid (electric bending with magnetic focusing) rings allow for simultaneous clock-wise and counter-clock-wise storage, enabling us to effectively deal with the major systematic error sources.