  We investigate several varying-mass dark-matter particle models in the
framework of phantom cosmology. We examine whether there exist late-time
cosmological solutions, corresponding to an accelerating universe and
possessing dark energy and dark matter densities of the same order. Imposing
exponential or power-law potentials and exponential or power-law mass
dependence, we conclude that the coincidence problem cannot be solved or even
alleviated. Thus, if dark energy is attributed to the phantom paradigm,
varying-mass dark matter models cannot fulfill the basic requirement that led
to their construction.
