  If the Ehrenfest time tau_E of a ballistic cavity is not negligible in
comparison to its dwell time tau_D, the weak localization correction to the
cavity's transmission is suppressed proportional to exp(-tau_E/tau_D). At the
same time, quantum interference enhances the probability of reflection into the
mode of incidence by a factor two. This `enhanced backscattering' does not
depend on the Ehrenfest time. We show that, in addition to the diagonal
enhanced backscattering, there are off-diagonal contributions to coherent
backscattering that become relevant if the Ehrenfest time is not negligible.
