Dielectric measurements of CsHSeO4 show a distinct relaxation at low frequencies at several isotherms (T < 363 K). For example, the relaxation frequency is around 4 kHz at 323 K and increases to higher frequencies (similar to 100 kHz) as the temperature increases. The relaxation has an activation energy of 0.8 eV. which is in close agreement with that associated with transport of charge carriers. We suggest that the observed dielectric relaxation could be produced by the H+ jump and SeO4-2 reorientation that cause distortion and change the local lattice polarizability, inducing dipoles like HSeO4-. (c) 2009 Elsevier B.V. All rights reserved.