  We consider non-perturbative effects at short distances in theories with
confinement. The analysis is straightforward within the Abelian models in which
the confinement arises on classical level. In all cases considered (compact
U(1) in 3D and 4D, dual Abelian Higgs model) there are non-perturbative
contributions associated with short distances which are due to topological
defects. In QCD case, both classical and quantum effects determine the role of
the topological defects and the theoretical analysis has not been completed so
far. Generically, the topological defects would result in 1/Q^2 corrections
going beyond the standard Operator Product Expansion. We review existing data
on the power corrections and find that the data favor existence of the novel
corrections, at least at the mass scale of (1-2) GeV. We indicate crucial
experiments which could further clarify the situation on the phenomenological
side.
