In this letter, we study the electronic structure and optical properties of the active medicinal component gamma-aminobutyric acid (GABA) and its cocrystals with oxalic (OXA) and benzoic (BZA) acid by means of the density functional theory formalism. It is shown that the cocrystallization strongly weakens the zwitter-ionic character of the GABA molecule leading to striking differences among the electronic band structures and optical absorption spectra of the GABA crystal and GABA: OXA, GABA: BZA cocrystals, originating from distinct sets of hydrogen bonds. Calculated band widths and Delta-sol band gap estimates indicate that both GABA and GABA:OXA, GABA:BZA cocrystals are indirect gap insulators. (C) 2013 Elsevier B.V. All rights reserved.