We have introduced the satellite hole spectral method to examine the binding sites of 3,3＇-diethyloxadicarbocyanine cation (DODC+) to various guanine-rich oligonucleotides. The satellite hole patterns along with normal mode calculations allow us to determine the interaction of DODC+ with a dimeric hairpin quadruplex formed by sequence d(G(4)T(4)G(4)). Our results are consistent with the groove binding model and eliminate the possibility of intercalation in the base pairs of guanine quartet.