  Diquark correlations are important in baryons, which can be modeled as
quark-diquark bound states. In addition, diquarks could play a role in
non-standard hadrons such as tetraquarks and pentaquarks. Here, we obtain
properties of these diquarks from the corresponding bound state equation, using
a model for the effective quark-quark interaction that has proved successful in
the light meson sector. Subsequently, we use the same model to estimate the
masses of the lightest diquark-diquark and diquark-antidiquark states.
