  We study the phenomenology of generic supergravity models in which gravity
mediation naturally competes with gauge mediation as the origin of
supergravity-breaking. This class of hybrid models has been recently motivated
in string inspired constructions and differs from usual gauge mediated
supersymmetry breaking models in having messenger masses of order of the GUT
scale. In these scenarios the gravitino can be the lightest supersymmetric
particle in wide regions of the parameter space and therefore a potential
candidate for dark matter. We investigate this possibility, imposing the WMAP
bound on its relic abundance and taking into account constraints from Big Bang
nucleosynthesis. We show that in these constructions viable gravitino dark
matter can be obtained in specific regions of the parameter space, featuring
large values of tan(beta) and where the supersymmetry breaking mechanism is
dominated by gauge mediation.
