In this paper we consider
the problem of deformation quantization of the algebra of polynomial functions on
coadjoint orbits of semisimple Lie groups. The deformation of an orbit is
realized by taking the quotient of the universal enveloping algebra of the
Lie algebra of the given Lie group, by a suitable ideal. A comparison with
geometric quantization in the case of SU(2) is done, where both methods
agree.