  In this article, we take the point of view that the $0^{++}$ nonet mesons
below $1 GeV$ are diquark-antidiquark states
$(qq)_{\bar{3}}(\bar{q}\bar{q})_3$, and devote to determine their masses in the
framework of the QCD sum rules approach with the interpolating currents
constructed from scalar-scalar type and pseudoscalar-pseudoscalar type diquark
pairs respectively. The numerical results indicate that the $0^{++}$ nonet
mesons may have two possible diquark-antidiquark substructures.
