  We extend the analysis of weak decays of heavy hadrons to the case of doubly
charmed baryons, \Xi_{cc}^{++}, \Xi_{cc}^{+} and \Omega_{cc}^{+}. Doubly
charmed baryons are modeled as a heavy-light system containing a heavy
cc-diquark and a light quark. Such a model leads to preasymptotic effects in
semileptonic and nonleptonic decays which are essentially proportional to the
meson wave function. Very clear predictions for semileptonic branching ratios
and lifetimes of doubly charmed baryons are obtained.
