  We study electronic image states around a metallic nanoring and show that the
interplay between the attractive polarization force and a repulsive centrifugal
force gives rise to Rydberg-like image states trapped several nanometers away
from the surface. The nanoring is modeled as a perfectly conducting isolated
torus whose electrostatic image potential is derived analytically. The image
states are computed via a two-dimensional finite-difference scheme as solutions
of the effective Schr\"odinger equation describing the outer electron subject
to this image potential. These findings demonstrate not only the existence of
detached image states around nanorings but allow us also to provide general
criteria on the ring geometry, i.e. the aspect ratio of the torus, that need to
be fulfilled in order to support such states.
