  The form factors of weak decays of the B_c meson to orbitally excited
charmonium, D, B_s and B mesons are calculated in the framework of the
QCD-motivated relativistic quark model based on the quasipotential approach.
Relativistic effects are systematically taken into account. The form factor
dependence on the momentum transfer is reliably determined in the whole
kinematical range. The form factors are expressed trough the overlap integrals
of the meson wave functions which are known from the previous mass spectra
calculations within the same model. On this basis semileptonic and nonleptonic
B_c decay rates to orbitally excited heavy mesons are calculated. Predictions
for the B_c decays to the orbitally and radially excited 2P and 3S charmonium
states are given which could be used for clarifying the nature of the recently
observed charmonium-like states above the open charm production threshold.
