The hopping mobility of charge carriers in disordered org. host-guest systems with a bimodal Gaussian d. of states is studied. Two semianal. models are used, viz. a relatively simple Mott-type model and a more advanced but computationally less efficient effective medium model. The latter model has been generalized, in order to be able to include the effect of different wave function extensions of the host and guest mols. It is shown that energetic disorder can result in a pronounced charge carrier concn. dependence of the mobility. This provides an explanation so far for unresolved issues concerning the guest concn. dependence of the measured hole mobility in some well-characterized host-guest systems. It is also argued that treating the mobility as a carrier concn. dependent quantity is highly relevant to the modeling of carrier transport in org. light emitting devices (OLEDs), consisting of an org. matrix material with embedded fluorescent or phosphorescent dye mols.