  We explore the parameter space of a Constrained Next-to-Minimal
Supersymmetric Standard Model with GUT scale boundary conditions (CNMSSM) and
find regions where the relic density of the lightest neutralino is compatible
with the WMAP measurement. We emphasize differences with the MSSM: cases where
annihilation of the LSP occurs via a Higgs resonance at low values of tan\beta
and cases where the LSP has a large singlino component. The particle spectrum
as well as theoretical and collider constraints are calculated with NMSSMTools.
All neutralino annihilation and coannihilation processes are then computed with
micrOMEGAs, taking into account higher order corrections to the Higgs sector.
