A shell-shaped children's seat for motor vehicles which is equipped with a headrest terminating in a backrest and with an impact member extending over the width of the shell and resting on the associated shell edge portions within the area of the seating surface; the impact member thereby extends rearwardly up to the transitional area of the backrest and the headrest, is pivotally connected thereat and can be tilted up visor-like after the disengagement of a locking device to facilitate ingress and egress of the seat.