The paper deals with the interpretation of the Mn2+ EPR spectra in the high-temperature phase of MgSiF6.6H(2)O. Two models are presented: the continuous and the discrete antiphase domain walls. Just above the ferroelastic phase transition, for each resonance transition two EPR lines are observed: the broad one and the narrow one. It is shown that the narrow line originates from centers lying inside the domains whereas the broader originates from the centers lying inside the domain walls.