The acid dissociation constants of some orthopalladated complexes have been determined in 10% v/v DMSO/water mixed solvent. The positive charge is located on the Pd(II) atom; in basic medium the H atom on the ligand is partially released, which convert these complexes into zwitterions, The ionization constants of the two overlapping equilibria of the HA-dppm-AH complex were evaluated by application of the separation method.