  We investigated the superfluid properties of the inner crust of neutron
stars, solving the Hartree-Fock-Bogoliubov equations in spherical Wigner-Seitz
cells. Using realistic two-body interactions in the pairing channel, we studied
in detail the Cooper-pair and the pairing-field spatial properties, together
with the effect of the proton clusters on the neutron pairing gap. Calculations
with effective pairing interactions are also presented, showing significant
discrepancies with the results obtained with realistic pairing forces. At
variance with recent studies on finite nuclei, the neutron coherence length is
found to depend on the strength of the pairing interaction, even inside the
nucleus. We also show that the Wigner-Seitz approximation breaks down in the
innermost regions of the inner crust, already at baryonic densities $\rho_b \ge
8 \cdot 10^{+13}$ g $\cdot$ cm$^{-3}$.
