The photochemical behaviour of some mixed ligand chromium(III) complexes with amino acids, [Cr(C 2 O 4 ) 2 (Aa)] n− (where Aa=alanine, valine, serine, cysteine, asparagine, aspartic acid) was studied. The attention was focused on the photoredox mode, which proceeded via inner- or intramolecular pathway yielding Cr(II) species and hydrated electrons, respectively. The secondary thermal processes were dependent on the O 2 presence and solution pH: (i) in oxygen-free media the regeneration of substrate and photoaquation induced by the Cr(III)→Cr(II) reduction were observed, (ii) in the presence of O 2 both Cr(II) and ligands were oxidized and the former was transformed not only into Cr(III) but also to Cr(VI) (provided that pH>7). Prolonged irradiation resulted in photoreduction of Cr(VI) accompanied by photodegradation of oxalate and/or amino-acid ligands. The photoreaction modes were independent of the co-ligand nature, but the secondary reaction rates and efficiencies were sensitive both to the co-ligand nature and its side substituent. Environmental consequences of the chromium photoreduction are discussed in the paper: the parameters affecting production and consumption of Cr(VI) are analysed, and the tools of controlling the photoredox behaviour of the Cr(III) and Cr(VI) compounds are suggested.