In this work, the values of pk(12) and pk(22) microdissociation constants of three aromatic amino acids (anthranilic (AA), N-methylanthranilic (MeAA) and N-phenylanthranilic (PhAA)) were calculated using density functional theory (DFT). Aqueous-phase energies and solvation energies were calculated using conductor-like polarizable continuum model (CPCM) of solvation. The results indicated that absolute differences between experimental and calculated pk values depend on combination of the polarization and diffuse functions and are quite different for pk(12) and pk(22) constants computated in the same level of theory. They demonstrate that some of the tested functionals and basis sets can accurately predict microdissociation constant (pk).