The invention relates to a control device (10) for a brake-power-assisted brake system of a vehicle having a first input device (26) for a supplied first information item (28) relating to a supplied assistance force (Fu) of a brake booster (14) of the brake-power-assisted brake system, a second input device (30) for a supplied second information item (32) relating to a total force (Fg) comprising the assistance force (Fu) and a driver braking force (Ff) supplied by activation of an activation element (12) of the brake-power-assisted brake system, an evaluation device (36) which is configured to define a third information item relating to a proportional relationship between the total force (Fg) and the assistance force (Fu) taking into account the first information item (28) and the second information item (32), and an output device (44, 50) which is configured to supply at least one control signal (46, 52) to at least one component (14, 54) of the brake-power-assisted brake system taking into account the defined third information item relating to the proportional relationship between the total force (Fg) and the assistance force (Fu). In addition, the invention relates to methods for operating a brake-power-assisted brake system of a vehicle.