We consider extensions of the Minimal Supersymmetric Standard Model (MSSM) where the extra
degrees of freedom interact weakly with the Higgs sector. These models allow to relax the tension
between the lower bound on the lightest CP even Higgs mass from direct LEP searches and the
theoretical upper bound of the MSSM. We study the beyond MSSM (BMSSM) effects via an
effective field-theory approach, assuming that the MSSM is valid up to a heavy physics scale M.
We compute the masses, couplings and branching fractions of the Higgs sector, including all the
relevant corrections up to order 1=M2. We find that the collider phenomenology can be greatly
different with respect to both the SM and the MSSM.