So far, the problem of harmful impact of vibrations on children when riding in safety seats in a car has not been sufficiently tackled. In the field of design of child safety seats, most effort was made to ensure safety during a collision because this is the main function of such seats. On the other hand, children significantly differ from adults in respect of their anatomy and physiology. The issue of the influence of vibrations on adult people’s bodies has been relatively well described, which is reflected in numerous normative acts having been adopted. For children, however, the studies on these issues are still at an early stage and there are no normative acts of this kind. The child should be treated in a special way, differently from the adult. The paper covers experimental tests related to the impact of vertical vibrations on the body of a child riding in a car in a safety seat. Results of road tests carried out for various road surface types as well as results of rig tests have been analysed and comparisons have been made in the frequency domain.