The present invention relates to fluorescent diketopyrrolopyrroles of the formula (I), or (III), a process for their preparation and their use for the preparation of inks, colorants, pigmented plastics for coatings, non-impact-printing material, color filters, cosmetics, polymeric ink particles, toners, as fluorescent tracers, in color changing media, in solid dye lasers, EL lasers and electroluminescent devices. A luminescent device comprising a compound, or composition according to the present invention is high in the efficiency of electrical energy utilization and high in luminance.