INTERFERENCE EFFECTS IN THE DECAY OF RESONANCE STATES IN THREE-BODY COULOMB SYSTEMS Oleg I. Tolstikhin,^1 Inga Yu. Tolstikhina,^2 and Chusei Namba^3 ^1 The Russian Research Center ``Kurchatov Institute'', Kurchatov sq. 1, Moscow, 123182, Russia ^2 P.~N.~Lebedev Physical Institute, Leninsky Prospect 53, Moscow, 117924, Russia ^3 National Institute for Fusion Science, Toki, 509-52, Japan Results of a systematic study of the lowest $^1S^e$ Feshbach resonance in symmetric three-body Coulomb systems are reported. We found that the resonance width oscillates as a function of the mass-ratio of the constituting particles and maybe even vanishes at certain values this parameter. These oscillations are interpreted as a result of the interference between two different paths of the resonance decay.