  Large - distance effects in the hadron wave function for the hadron-Pomeron
vertex in the QCD -model are discussed. It is shown that they lead to the
spin-flip part of the Pomeron coupling which can reach $10 \div 20 %$ with
respect to the non-flip part. The obtained structure of the Pomeron coupling
modifies spin asymmetries in high--energy diffractive reactions where the
Pomeron structure becomes determinative. We study spin asymmetries in exclusive
reactions and in the diffractive $Q \bar Q$ and $J/\Psi$ production. We have
found that spin effects in these diffractive processes are sensitive to the
spin-flip part of the Pomeron coupling.
