  In this paper, we try to generalize to the case of compact Riemannian
orbifolds $Q$ some classical results about the existence of closed geodesics of
positive length on compact Riemannian manifolds $M$. We shall also consider the
problem of the existence of infinitely many geometrically distinct closed
geodesics.
  In the classical case the solution of those problems involve the
consideration of the homotopy groups of $M$ and the homology properties of the
free loop space on $M$(Morse theory). Those notions have their analogue in the
case of orbifolds (see [7]). The main part of this paper will be to recall
those notions and to show how the classical techniques can be adapted to the
case of orbifolds.
