A new kind of bifunctional reagent was used for carbon electrode modification : condensed aromatic rings were used as an anchor group for chemisorption on the basal surface of the carbon electrode and chemically active functional groups were used to immobilize organic compounds via amino or thiol functional groups. Spontaneous and selective immobilization of naphthoquinones with an -NH2 or -SH group at the end of the side-chain was achieved, and the monolayer of immobilized quinones showed a reversible electrochemical process. Application of this modified electrode for the immobilization of proteins (enzymes) via lysine or cysteine amino acid residuals is suggested.