  We discuss constrained and semi--constrained versions of the
next--to--minimal supersymmetric extension of the Standard Model (NMSSM) in
which a singlet Higgs superfield is added to the two doublet superfields that
are present in the minimal extension (MSSM). This leads to a richer Higgs and
neutralino spectrum and allows for many interesting phenomena that are not
present in the MSSM. In particular, light Higgs particles are still allowed by
current constraints and could appear as decay products of the heavier Higgs
states, rendering their search rather difficult at the LHC. We propose
benchmark scenarios which address the new phenomenological features, consistent
with present constraints from colliders and with the dark matter relic density,
and with (semi--)universal soft terms at the GUT scale. We present the
corresponding spectra for the Higgs particles, their couplings to gauge bosons
and fermions and their most important decay branching ratios. A brief survey of
the search strategies for these states at the LHC is given.
