The effects of Na+, K+, Li+ and Mg2+ cations on the fluorescence spectra of benzoCrown-4, benzoCrown-5, and benzoCrown-6 were investigated in dry acetonitrile. The alkali cation coused the complexation enhanced quenched fluorescence (CEQF) by increasing the fluorescence quenching rates of the cationic fluoroionophores. The 1:1 stoichiometry of ion association constants, InKa have been obtained. The results were ruled out by compatibility of cationic radii and macrocycle size. The order of InKa found for benzocrown-5 was Mg+>Na+>Li+ for the cations and the Na+>Li+ was found for benzocrown-6. The most of the cations have slight effects on the fluorescence spectra of benzocrown-4 in acetonitrile.