  One aim of cosmic ray measurements is the search for possible signatures of
annihilating or decaying dark matter. The so-called positron excess has
attracted a lot of attention in this context. On the other hand it has been
proposed that the data might challenge the established diffusion model for
cosmic ray propagation. We investigate an inhomogeneous diffusion model by
solving the corresponding equations analytically. Depending on the propagation
parameters we find that the spectral features of the positron spectrum are
affected significantly. We also discuss the influence of the inhomogeneity on
hadronic spectra.
