  We study the relation between vertex operators in AdS_5 x S^5 and classical
spinning string solutions. In the limit of large quantum numbers the treatment
of vertex operators becomes semiclassical. In this regime, a given vertex
operator carrying a certain set of quantum numbers defines a singular solution.
We show in a number of examples that this solution coincides with the classical
string solution with the same quantum numbers but written in a different
two-dimensional coordinate system. The marginality condition imposed on an
operator yields a relation between the energy and the other quantum numbers
which is shown to coincide with that of the corresponding classical string
solution. We also argue that in some cases vertex operators in AdS_5 x S^5
cannot be given by expressions similar to the ones in flat space and a more
involved consideration is required.
