  Exclusive semileptonic B decays to radially excited charmed mesons are
investigated at the first order of the heavy quark expansion. The arising
leading and subleading Isgur-Wise functions are calculated in the framework of
the relativistic quark model. It is found that the 1/m_Q corrections play an
important role and substantially modify results. An interesting interplay
between different corrections is found. As a result the branching ratio for the
B-> D'e\nu decay is essentially increased by 1/m_Q corrections, while the one
for B-> D*'e\nu is only slightly influenced by them.
