Different (iso)guanosine-based self-assembled ionophores give distinctly different results in extraction experiments with alkali(ne earth) cations. A lipophilic guanosine derivative gives good extraction results for K + , Rb + , Ca 2+ , Sr 2+ , and Ba 2+ and in competition experiments it clearly favors the divalent Sr 2+ (and Ba 2+ ) cations. 1,3-Alternate calix[4]arene tetraguanosine hardly shows any improvement in the extraction percentages compared to its reference compound 1,3-alternate calix[4]arene tetraamide. This indicates that one G-quartet does not provide efficient cation complexation under these conditions. In the case of the lipophilic isoguanosine derivative there is a cation size dependent affinity for the monovalent cations (Cs + ≫Rb + ≫K + ), but not for the divalent cations (Ca 2+ >Ba 2+ >Sr 2+ >Mg 2+ ). In competition experiments the isoguanosine derivative, unlike guanosine, does not discriminate between monovalent and divalent cations, giving an almost equal extraction of Cs + and Ba 2+ .