the back seat in the new challenger is not that big but you can add a car seat to it safely,i doubt anyone knows the exact measurements of it but my neighbor owns an 09 model and it has plenty of room for a car seat,its just not practical car to drive every day the thieves are having a good old time trying to steal those cars right now,good luck.here's all the specs on that car if you want to look them over,click on the year and see,http://www.automedia.com/2009-New-Car-Buyers-Guide/2009-Dodge-Challenger-Coupes/trim/?utm_source=YSM&utm_medium=YSM_YSM_Dodge_SS&OVRAW=2009%20dodge%20challenger%20specs&OVKEY=2009%20dodge%20challenger%20specs&OVMTC=standard&OVADID=43349247522&OVKWID=215615648522