An analysis of road accident reports and surveys concerning this issue show that children aged from 8 to 12 years are often improperly carried in cars. In defiance of the regulations in force, some parents protect their children exclusively by fastening the standard seat belts intended for adults. The paper presents an analysis of results of experimental tests aimed at the assessment of influence of the type of a chiId restraint system (CRS) used on the effectiveness of operation of a seat belt during a frontal impact. Attention was focused on the positioning of the seat belt in relation to the child in association with the dynamic load and kinematics of the child. The experiments were carried out with the use of a P10 test dummy representing a child aged about 10 years. Three CRS types used with the test dummy were considered: the dummy was placed directly on the car seat, on a booster Cushion (without a backrest), and on a booster seat (with a backrest). The dummy was fastened with the use of a standard seat belt. The experiments were carried out on a crash test stand at the Automotive Industry Institute (PIMOT) in Warsaw. The results obtained have revealed important relations between the CRS type used and the observed loads of the head and torso of the dummy. They have confirmed that the child protection should not be Iimited to mere use of a seat belt for adults because the seat belt positioning in relation to the child's body not only adversely affects the effectiveness of the seat belt operation but also may cause injuries to child's abdomen and neck.