Three square-pyramidal complexes of dioxidovanadium(V) with pyridoxalaminoguanidine (PLAG), of the formulas NH4[VO2(PLAG?2H)]?H2O (1), VO2(PLAG?H) (2) and K[VO2(PLAG?2H)]?H2O (3) have been synthesized and characterized by IR and UV-Vis spectral analysis and in case of 1 and 3 by X-ray crystallography as well. The reaction of aqueous ammoniacal solution of NH4VO3 and PLAG resulted in formation of 1, which in MeOH undergoes spontaneous transformation into 2, which, in turn, in the reaction with KOH transforms into 3. In these complexes PLAG is coordinated in a common tridentate ONN mode, via phenoxide oxygen atom and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In all previously characterized complexes PLAG was coordinated in neutral form. However, here we have proven that this ligand can be coordinated in both mono- (2) and doubly deprotonated form (1 and 3) as well. [Projekat Ministarstva nauke Republike Srbije, br. 172014].