A quantum analogue of the dual pair (sl(2), O-n) is constructed and it
s detailed investigation is worked out. The main results include a qua
ntum version of the theory of spherical harmonics, the Capelli identit
y, and the first fundamental theorem of invariant theory. Also a descr
iption of Casimir elements of the twisted q-deformed algebra U-q(O-n)
is given in relation to the Reflection Equations.