  The analysis of singly charmed hadrons has been extended to the case of
doubly charmed baryons, $\Xi_{cc}^{++}$, $\Xi_{cc}^{+}$ and $\Omega_{cc}^{+}$.
Doubly charmed baryons are described as a system containing a heavy
$cc$-diquark and a light quark, similarly as in a heavy-light meson. This leads
to preasymptotic effects in semileptonic and nonleptonic decays which are
essentially proportional to the meson wave function. Interplay between
preasymptotic effects in semileptonic and/or nonleptonic decay rates leads to
very clear predictions for semileptonic branching ratios and lifetimes of
doubly charmed baryons.
