Recent findings suggest to split the impulse response of the radio channel into discrete paths and the "diffuse multipath" (DMP). This diffuse part can be described by an exponentially decaying power delay profile. This paper shows how to improve current radio channel models using the DMP concept. From MIMO channel measurements, we find that the DMP parameters are strongly correlated with the parameters of the discrete paths. This holds for various (indoor) environments. We provide a simple way to model the statistics of the DMP parameters. Finally, we include the DMP concept in a novel MIMO model, the Random-Cluster model. We find that including DMP significantly improves the model fit in terms of mutual information and channel diversity.