A non-aqueous pigment dispersion includes a diketopyrrolo-pyrrole pigment, a polymeric dispersant, and a dispersion synergist in a non-aqueous dispersion medium wherein the dispersion synergist is a diketopyrrolo-pyrrole derivative according to Formula (I): ##STR00001## wherein R.sup.1, R.sup.2, and R.sup.3, are independently selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, an tert.-butyl group, a phenyl group, a cyano group, and an acid group; R.sup.4-, R.sup.5, and R.sup.6 are independently selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, an tert.-butyl group, a phenyl group, and a cyano group; and wherein one of R.sup.7 and R.sup.8 is a group including two acid functions while the other one of R.sup.7 and R.sup.8 represents hydrogen.