  We argue that multi-trace deformations of the boundary CFT in AdS/CFT
correspondence can arise through the OPE of single-trace operators. We work out
the example of a scalar field in AdS_5 with cubic self interaction. By an
appropriate reparametrization of the boundary data we are able to deform the
boundary CFT by a marginal operator that couples to the conformal anomaly. Our
method can be used in the analysis of multi-trace deformations in N=4 SYM where
the OPEs of various single-trace operators are known.
