  The cold dark matter scenario predicts that a large number of dark subhalos
should be located within the halo of each Milky-way sized galaxy. One tell-tale
signature of such dark subhalos could be additional milliarcsecond-scale image
splitting of quasars previously known to be multiply-imaged on arcsecond
scales. Here, we estimate the image separations for the subhalo density
profiles favoured by recent N-body simulations, and compare these to the
angular resolution of both existing and upcoming observational facilities. We
find, that the image separations produced are very sensitive to the exact
subhalo density profile assumed, but in all cases considerably smaller than
previous estimates based on the premise that subhalos can be approximated by
singular isothermal spheres. Only the most optimistic subhalo models produce
image separations that would be detectable with current technology, and many
models produce image separations that will remain unresolved with all
telescopes expected to become available in the foreseeable future. Detections
of dark subhalos through image-splitting effects will therefore be far more
challenging than currently believed, albeit not necessarily impossible.
