Diketopyrrolopyrroles (DPP) are well-known organic pigments. The title compound (DPPP) is one of DPP derivatives that shows a high proton affinity because of the N atoms of the pyridyl ring. Protonation at the N-site brings about a variety of changes in color as well as in electrical and photoelectrical conductivities. Two crystal modifications have been found to exist: DPPP I (grown from vapor phase) and DPPP II (grown from solution). Structure analysis revealed that there is a striking difference in intermolecular hydrogen bonds between two modifications: DPPP I is characterized only by NH…O hydrogen bonds whereas DPPP II include two of the H-bond based on NH…N and NH…O.