  It is known that the cosmological baryon density ($\Omega_{\rm{b}}$) and dark
matter density ($\Omega_{\rm{dm}}$) have strikingly similar values. However, in
most theories of the early Universe, each density is explained by separate
dynamics and consequently there is no compelling reason for this observation.
In this note, I briefly review a model in which the dark matter species
possesses a particle-antiparticle asymmetry. This asymmetry determines both the
baryon asymmetry and strongly affects the dark matter density, thus naturally
linking $\Omega_{\rm{b}}$ and $\Omega_{\rm{dm}}$. In these models it is shown
that sneutrinos can play the role of such dark matter.
