  We reinterpret and extend some old work on CFT/string duality. We consider
some asymptotically conformal field theory in large N limit, with conformal
symmetry broken by VEV's of infinite number of operators. Assuming that this
theory confines (i.e. is dual to infinite number of free composite particles)
we derive explicit equation for the mass spectrum operator Q of the theory,
relating this operator to terms OPE expansion of CFT. Under some general
assumptions about growth of OPE coefficients (less than double factorial
growth) the resulting expansion for the mass spectrum is convergent. This
method applies to confining CFT of ADS family as well as any asymptotically CFT
with confinement. This includes the ordinary QCD. In the latter case the first
terms of our perturbation expansion have good correspondence with experimental
Regge trajectories at low angular momentum.
