  We present a comparison of the properties of substructure halos (subhalos)
orbiting within host halos that form in Cold Dark Matter (CDM) and Warm Dark
Matter (WDM) cosmologies. Our study focuses on selected properties of these
subhalos, namely their anisotropic spatial distribution within the hosts; the
existence of a "backsplash'' population; the age-distance relation; the degree
to which they suffer mass loss; and the distribution of relative (infall)
velocities with respect to the hosts. We find that the number density of
subhalos in our WDM model is suppressed relative to that in the CDM model, as
we would expect. Interestingly, our analysis reveals that backsplash subhalos
exist in both the WDM and CDM models. Indeed, there are no statistically
significant differences between the spatial distributions of subhalos in the
CDM and WDM models. There is evidence that subhalos in the WDM model suffer
enhanced mass loss relative to their counterparts in the CDM model, reflecting
their lower central densities. We note also a tendency for the (infall)
velocities of subhalos in the WDM model to be higher than in the CDM model.
Nevertheless, we conclude that observational tests based on either the spatial
distribution or the kinematics of the subhalo population are unlikely to help
us to differentiate between the CDM model and our adopted WDM model.
