Mixed Dark Matter and the Fate of Baryon and Lepton Symmetries

The available data on large scale structures seem to favour models with mixed dark matter (MDM), i.e. with a hot and cold component in a rather well--defined amount, or with some form of ``warm" dark matter. I discuss some prospects for these new scenarios for DM in the context of supersymmetric extensions of the electroweak standard model. In particular, I emphasize the intriguing link which exists between the present prospects of solution of the DM puzzle and the explicit or spontaneous breaking of baryon and/or lepton number symmetries. Some consequences on the issue of baryogenesis are worked out.