The synthesis of novel dibenzo-24-crown ether substituted nitroxides and their use as spin probes for the detection of cation guests by EPR are reported. Formation of a host-guest complex between the proposed spin probes and several cations, both organic and inorganic, was evidenced by a significant change in the value of the benzylic and nitrogen EPR hyperfine splittings upon complexation. This favorable feature provided a reliable EPR sensor that is able to selectively distinguish different cationic guests.