The stabilization method is used in conjunction with Koopmans-based approximation to calculate the energies of pi* temporary anion states of a series of substituted benzenes in density functional theory. In this approach, the Koopmans expression is corrected due to the consideration of the integer discontinuities in the exact exchange-correlation potential. Stabilization is accomplished by varying the exponents of appropriate diffuse functions. The energies of pi* states are then identified by investigating the relationship between the resultant eigenvalues and scale parameter. Results indicate that this approach can yield an improvement in the predictions of the absolute energies of pi* states over other methods.