The crystal structures of six novel salts of 4-nitrobenzoic acid - namely, 2-hydroxyethylammonium 4-nitrobenzoate (I), 2-hydroxypropylammonium 4-nitrobenzoate (II), 1-(hydroxymethyl)propylammonium 4-nitrobenzoate (III), 3-hydroxypropylammonium 4-nitrobenzoate (IV), bis-(2-hydroxyethylammonium) 4-nitrobenzoate (V), morpholinium 4-nitrobenzoate (VI) - containing the same anion but different cations have been studied. The ionic forms of I-VI serve as building blocks of the supramolecular architecture, and in crystals they are held together via ionic N-H⋯O and O-H⋯O hydrogen bonds. In the crystal packing the building blocks of I-III are self-assembled via N-H...O, O-H⋯O and C-H...O hydrogen bonds to form the chains which are further consolidated into two-dimensional layers by the same type of interactio ns. In IV-VI the chain-like structures have been generated by building blocks.