  We calculate three-loop corrections to correlation functions of heavy-quark
currents in the low- and high-energy regions. We present 30 coefficients both
in the low-energy and the high-energy expansion of the scalar and the vector
correlator with non-diagonal flavour structure. In addition we compute 30
coefficients in the high-energy expansion of the diagonal vector, axial-vector,
scalar and pseudo-scalar correlators. Possible applications of our new results
are improvements of lattice-based quark-mass determinations and the approximate
reconstruction of the full momentum dependence of the correlators.
