  We discuss the specific features of extracting properties of the exotic
polyquark hadrons (tetraquarks, pentaquarks) compared to the usual hadrons by
the QCD sum-rule approach. In the case of the ordinary hadrons, already the
one-loop leading-order correlation functions provide the bulk of the hadron
observables, e.g., of the form factor; inclusion of radiative corrections
modifies already nonzero one-loop contributions. In the case of an exotic
hadron, the situation is qualitatively different: discussing strong decays of
an exotic tetraquark meson, which provide the main contribution to its width,
we show that the disconnected leading-order diagrams are not related to the
tetraquark properties. For a proper description of the tetraquark decay width,
it is mandatory to calculate specific radiative corrections which generate the
connected diagrams.
