The main aims of the current study were to (1) investigate misuse and/or inappropriate use across different booster seat types (including high back booster seats, booster seat cushions, and booster seats/cushions used in combination with an H-harness) through an Australian CRS/booster seat inspection program conducted between October 2004 and October 2011, and (2) determine whether misuse and/or inappropriate use across booster seat types changed following the introduction in 2009 of new Australian CRS/booster seat and motor vehicle restraint use legislation for children aged 7years and under. Results reveal high levels of booster seat misuse among booster seats (including high back booster seats, booster seat cushions, and booster seats/cushions used in combination with an H-harness) installed in Australian motor vehicles that present at CRS inspection clinics. Of all the booster seats inspected, almost two thirds (62 ) were reported as having at least one instance of misuse, with almost all aspects of the booster seat misused in some way. Misuse was highest for booster seats/cushions used in combination with an H-harness (84 ), compared to booster cushions (63 ) and high back booster seats (55 ). Of the 792 booster seats inspected, 673 (85 ) were inspected before, and 119 (15 ) were inspected following, the introduction of the new CRS legislation. While it was not possible to ensure similarity between components of the sample observed in the pre- and post-legislation periods, significantly more misuse and inappropriate use was observed in the post-legislation component of the sample.