Child restraint systems (CRS) for vehicles are designed to provide specialized protection for child occupants in the event of a crash. The effectiveness of these restraint systems is influenced by many variables including the way that children are positioned in their CRS. This study used a naturalistic, observational approach to examine how children are restrained and seated in their restraint systems, including booster seats, while travelling in a car. Children‟s out-of-position status was judged as out of the protective zone provided by the CRS structure or otherwise away from the optimal/preferred location within the CRS or vehicle restraint system. Families with children aged between 1 and 8 years drove an instrumented 'study vehicle' on their regular trips for 3 weeks. A discrete video recording system in the vehicle provided images of the driver and front seat passenger, the rear seat child passengers and the traffic ahead. Video-recordings were analysed for 92 trips undertaken by 12 families including 25 children and 19 drivers. The mean trip duration was approximately 19 minutes (SD=30 min), with the duration ranging from approximately 2 minutes to 3.6 hours. Most trips were undertaken with the mother driving (65%) and without a front seat passenger (65%). Trips were predominantly undertaken in urban areas (96%), on suburban roads/streets (93%), and under low complexity traffic conditions (92%). At least one out-of-position event was observed on all (100%) of the 92 trips. On average, children were out-of-position approximately 70% of the journey time. These findings have important implications for children‟s protection in crashes as arguably their out-of-position status results in sub-optimal restraint and can reduce or nullify the safety benefits of CRS.