  We study heavy quarkonium within the light-front Hamiltonian formalism. Our
effective Hamiltonian is based on the holographic QCD confining potential and
the one-gluon exchange interaction with a running coupling. The obtained
spectra are compared with experimental measurements. We present a set of
light-front wave functions, which exhibit rich structure and are consistent
with the nonrelativistic picture. Finally, we use the wave functions to compute
the charge and mass radii.
