Narrow Polar Rings versus Wide Polar Ring/Disk Galaxies
  In the latest ten years, a big effort has given to study the morphology and
kinematics of polar ring galaxies: many steps forward and new discoveries on
the structure and formation mechanisms for such systems have been made during
this time thanks to high resolution photometric and spectroscopic data. In this
paper, I review the latest results obtained for this class of galaxies, from
both observational and theoretical studies. I focus on the analysis of the
observed properties (e.g., structure, colours, age, metallicity, and
kinematics) for narrow and wide polar ring galaxies. In particular, I compare
AM2020-504 and NGC4650A, which are the two prototypes for narrow and wide polar
rings, respectively. I discuss similarities and differences between the two
kinds of systems and how they reconcile with the main formation scenarios
proposed for this class of galaxies.
