  We describe the finite volume effects of CP-odd quantities, such as the
neutron electric dipole moment and the anapole moment in the $\theta$-vacuum,
under different topological sectors. We evaluate the three-point Green's
functions for the electromagnetic current in a fixed non-trivial topological
sector in order to extract these CP-odd observables. We discuss the role of
zero modes in the CP-odd Green's function and show that, in the quenched
approximation, there is a power divergence in the quark mass for CP-odd
quantities at finite volume.
