  We argue that parton distributions in coordinate space provide a more natural
object for nonperturbative methods compared to the usual momentum distributions
in which the physics of different longitudinal distances is being mixed. To
illustrate the advantages of the coordinate space formulation, we calculate the
coordinate space distributions for valence quarks in the proton using the QCD
sum rule approach. A remarkable agreement is found between the calculated and
the experimentally measured u-quark distribution up to light-cone distances
$\Delta^- = \Delta^0 - \Delta^3$ of order $\sim 1$ fm in the proton rest frame.
The calculation for valence d quarks gives much worse results; the reasons for
this discrepancy are discussed.
