We discuss the close relation between shadowing in deep-inelastic lepton-nu
cleus scattering and diffractive photo- and leptoproduction of hadrons from
free nucleons. We show that the magnitude of nuclear shadowing at small Bj
orken-x, as measured by the E665 and NMC collaborations, is directly relate
d to HERA data on the amount of diffraction in the scattering from free nuc
leons.