  In this talk we reexamine the possibility of evaluating parton distribution
functions from lattice simulations. We show that, while in principle individual
moments can be extracted from lattice data, in all cases the process of
renormalization, hindered by lattice momenta limitation, represents an
obstruction to a direct calculation of the full parton distribution function
from QCD simulations. We discuss the case of the Ji quasi-parton distribution
functions, the possibility of using the reduced Ioffe-time distributions and
the more recent proposal of directly subtracting power divergent mixings in
perturbation theory.
