  We test the validity of the QCD sum rules applied to the light scalar mesons,
the charmed mesons $D_{s0}(2317)$ and $D_{s1} (2460)$, and the X(3872) axial
meson, considered as tetraquark states. We find that, with the studied
currents, it is possible to find an acceptable Borel window only for the
X(3872) meson. In such a Borel window we have simultaneouly a good OPE
convergence and a pole contribution which is bigger than the continuum
contribution. We interpret these results as a strong argument against the
assignment of a tetraquark structure for the light scalars and the
$D_{s0}(2317)$ and $D_{s1} (2460)$ mesons.
