Accurate yet computationally e cient models of aqueous solvation represents an important challenge to molecular modeling. Continuum solvation models such as the polarized continuum model (PCM), the conductor-like screening model (COSMO), and the universal SMx models o er a computational e cient model of solvation for molecules treated with electronic structure methods. While the accuracy of these and related methods have been studied extensively using DFT and wavefunction-based methods, there has been relatively little work on corresponding studies with semiempirical methods. In this paper we study the accuracy of using AM1 , PM3 , PM6 , and DFTB together with the SMD continuum solvation model using the MNSOL data set and present new parameters that increase the accuracy considerably for polar solvents. This manuscript is organized as follows. After a presentation of our computational methodology we discuss the accuracy of the semiempirical SMD calculations using the radii optimized for ab initio methods. We then compare several sets of reoptimized radii and select the best set. We show that the new radii lead to more accurate pKa predictions as well as more accurate solvation free energies for DMSO, acetonitrile, and methanol.