  We show that both the multiplicity distribution and the ratio of factorial
cumulants over factorial moments for 2-jet events in e+e- annihilation at the
Z^0 peak can be well reproduced by the weighted superposition of two negative
binomial distributions, associated to the contribution of $b\bar b$ and light
flavoured events respectively. The negative binomial distribution is then
suggested to describe the multiplicity distribution of 2-jet events with fixed
flavour.
