  Quantum coherence of electrons interacting via the magnetostatic coupling and
confined to a mesoscopic cylinder is discussed.
  The electromagnetic response of a system is studied. It is shown that the
electromagnetic kernel has finite low frequency limit what implies infinite
conductivity. It means that part of the electrons is in a coherent state and
the system can be in general described by a two-fluid model.
  The coherent behavior is determind by the interplay between finite size
effects and the correlations coming from the magnetostatic interactions (the
interaction is considered in the mean field approximation).
  The related persistent currents depend on the geometry of the Fermi Surface.
If the Fermi Surface has some flat portions the self-sustaining currents can be
obtained.
  The relation of the quantum coherent state in mesoscopic cylinders to other
coherent phenomena is discussed.
