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Numerical studies are made on the Matusbara-Toyazawa model for structurally disordered systems. The criterion for localization proposed by Edwards and Thouless is applied to finite two dimensional impurity lattices of various sizes. The ratio L of the energy shift due to the change of boundary condition to the spacing between adjacent levels is taken to be a measure of the degree of localization for each level. Large dispersion in L found at intermediate and low concentration regions indicates the coexistence of both localized and nonlocalized states in disordered systems with strongly dispersed density of states. It is found that localization occurs far more easily in the high energy edges rather than in low energy tail. This is due to the weak coupling between the anti-bounding orbital states of cluster molecules. Some numerical results are also presented on the effect of additional potential fluctuation at lattice sites.