The fluorescent probes pyrene and RU(bpy)(3)(2+) were used to study the relative locations of cations and anions in microphase separated perfluorinated ionomers. After determining that these probes are located in the interfacial regions that separate the fluorocarbon phase from the ion and water-rich phase, cationic and anionic quencher ions were introduced into the system and changes in fluorescence monitored. Results show that Cs’ is located on the aqueous side of the interfacial region, in close proximity to pyrene, while I- is located deeper into the interfacial region and farther away from the aqueous phase. These differences are greater for carboxylate ionomers than for sulfonate ionomers, in close parallel to their relative abilities to discriminate against anion transport in practical membrane-based applications. These results show that the phenomenon of superselectivity is based on the differences in the average locations and therefore the transport pathways of cations and anions in perfluorinated ionomers.