  Virtual photons have both the transverse and longitudinal polarization. In
the inclusive DIS the impact of longitudinal photons, quantified by
R=sigmaL/\igmaT sim 0.2, is marginal, but in diffractive DIS with excitation of
small mass hadronic states or exclusive diffraction into vector mesons, QCD
predicts R >> 1 in agreement with the experiment. After a brief review of the
modern status of QCD theory of diffractive vector meson production I argue that
longitudinally polarized gluons give rise to a large longitudinal polarization
of the prompt JPsi and Psiprim observed at the Tevatron.
