A method for operating an exhaust gas treatment device including an electric heater for heating an exhaust gas flow in the exhaust gas treatment device and/or a surface in the exhaust gas treatment device and a feed point for feeding an additive into the exhaust gas treatment device to impinge upon the electric heater, includes supplying additives to the feed point, determining an operational state of the exhaust gas treatment device, in which deposits can impinge upon the electric heater, using at least one state variable, determining a cycle frequency in dependence on the operating state when the operating state lies in a predetermined operating state range, and cyclically activating and deactivating the electric heater using the determined cycle frequency when the determined operating state lies in the predetermined operating state range. A motor vehicle having the exhaust-gas treatment device is also provided.