EPR spectroscopy has been applied to investigate the europium(II) sites in europium(II)-doped aluminate phosphors with tridymite structure. X-band spectra of the phosphors are quite complicated to analyse due to large zero-field splittings, so that little information about europium(II) ions can be obtained. On the contrary, high-frequency EPR measured at 90 or 180 GHz shows symmetric spectra centred around about g=2.0. The spectral simulation confirmed there that is one site in the CaAl_2O_4, three in the SrAl_2O_4 and two in the BaAl_2O_4 in contrast to our expectations from crystallographic sites.