  The relic abundance of the lightest right-handed sneutrino dark matter in
supersymmetric B-L extension of the standard model is revisited. We argue that
it can form a bound state through the exchange of light B-L Higgs boson and a
large non-perturbative Sommerfeld effect is obtained. We emphasized that with
this effect the relic abundance of right-handed sneutrino will lie within the
observational limits and the right-handed sneutrino will remain a viable dark
matter candidate of mass order up to 1.5 TeV.
