  The problem of the lightest Higgs boson mass in the next-to-minimal
supersymmetric standard model (NMSSM) is investigated. Assuming the validity of
the perturbation theory up to unification scales and using the recent
experimental results for the top quark mass, the restrictions on the NMSSM
coupling constants are obtained. These restrictions are used to make the
predictions for the lightest Higgs mass, which are compared to those of the
minimal supersymmetric standard model (MSSM).
