  In this paper we consider embedded eigenvalues of a Schroedinger Hamiltonian
in a waveguide induced by a symmetric perturbation. It is shown that these
eigenvalues become unstable and turn into resonances after twisting of the
waveguide. The perturbative expansion of the resonance width is calculated for
weakly twisted waveguides and the influence of the twist on resonances in a
concrete model is discussed in detail.
