The electrochemical characteristics are reported for two constitutional isomers of porphyrin, hemiporphycene and isoporphycene. Each of the two isomers was studied as the neutral free base, and as metal(II) complexes (M = Ni and Cu). Further these redox characteristics were compared, and found qualitatively similar to those already known for porphyrin and two other isomers, namely corrphycene 4 and porphycene 2, although significant changes were observed in the reduction potentials.