  Each lens space has a canonical contact structure which lifts to the
distribution of complex lines on the three-sphere. In this paper, we show that
a symplectic homology cobordism between two lens spaces, which is given with
the canonical contact structure on the boundary, must be diffeomorphic to the
product of a lens space with the unit interval. As one of the main ingredients
in the proof, we also derive in this paper the adjunction and intersection
formulae for pseudoholomorphic curves in an almost complex 4-orbifold,
extending the relevant work of Gromov and McDuff in the manifold setting.
