  I discuss exclusive production of the $\eta'$, $J/\psi$, and $\chi_c(0^+)$
mesons in $pp$ and $p \bar p$ collisions at high energies. QCD diffractive
mechanisms as well as nondiffractive mechanisms are discussed. Different
unintegrated gluon distribution functions (UGDF) are used. Some differential
distributions are shown and discussed.
