Contemporary research has pointed out the differences observed in the kinematics of pediatric dummies and rear‐facing child restraint systems (CRS) between the regulatory bench used in FMVSS 213 and CMVSS 213 regulations and real vehicle seats. The objective of this study was to compare the performance of forward‐facing CRS between a variant of the ECE R44 bench and a production seat vehicle. Two different Anthropomorphic Test Device (ATD) sizes (P3 and P6) using the same child restraint system, a non‐Isofix highback booster seat, were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Three repeats per ATD and mounting seat were done, resulting in a total of 12 tests. A matched‐pair statistical analysis R44 bench to vehicle seat was performed. Statistically significant differences associated with the mounting seat were observed in the kinematic responses of the ATD and the CRS. A 3D motion tracking system allowed identifying differences in the sagittal, transverse and frontal trajectories of the center of gravity of the head between the ECE R44 and the vehicle seat. It was observed that the use of the high‐back booster on the vehicle seat improved the resultant accelerations of the head and thorax and reduced the motion of the head CG.