  The properties of the Theta^{+} and Xi^{--}_{3/2} exotic baryons have been
investigated in the framework of diquark- diquark-antiquark system. A model for
diquark suggested in an analogy with the quasi-particle in a crystal lattice
has been used. The mass of the exotics have been computed. The Decay width of
the Theta^{+} has been estimated to be ~ 11 MeV using effective diquark theory.
The radius of the Xi^{--}_{3/2} has been extracted as 0.94fm using the
experimental value of the frac{\Gamma_{\Theta^{+}}}{\Gamma_{\Xi^{--}_{3/2}}}.
The results obtained are found to be in good agreement with the present
experimental and theoretical suggestions.
