Abstract <p>The electrochemical behavior of a series of isomers of methoxyphenoxy derivatives of cobalt phthalocyanine {CoPc[4-(<i>x</i>-OСH₃OPh)]₄ and CoPc[3-(<i>x-</i>OСH₃OPh)]₄, where <i>x</i> = 4′, 3′, or 2′} in alkaline aqueous solutions, and also of ZnPc[4-(<i>x-</i>OСH₃OPh)]₄, where <i>x</i> = 4′, 3′, or 2′, in the CH₂Cl₂ medium is studied for the first time using cyclic voltammetry. The electrochemical behavior and the electrocatalytic activity of cobalt phthalocyanines in the reaction of dioxygen electroreduction is analyzed depending on the functional substitution in the macrocycle molecule. For CoPc[4-(<i>x-</i>OСH₃OPh)]₄ and CoPc[3-(<i>x-</i>OСH₃OPh)]₄, the processes of oxidation (Co²⁺ ↔ Co³⁺) and reduction (Co²⁺ ↔ Co¹⁺) of the central metal ion are observed as well as two sequential stages of the one-electron electroreduction of the phthalocyanine ligand. It is found that these cobalt phthalocyanine derivatives can serve quite efficiently as the systems for dioxygen electroreduction. For ZnPc[4-(<i>x-</i>СH₃OPh)]₄, where <i>x</i> = 4′, 3′, or 2′, the formation of polyphthalocyanine films is observed during the monomer electrooxidation in dichloromethane.</p>