I'm pretty sure it needs an adapter for all car seats, it looks like the bar adapter you'd get for a bob stroller, however it makes different ones for different seats and is more affordable than the bob adapter, especially considering all the other features come standard with the stroller: http://www.amazon.com/Joovy-Zoom-Seat-Adapter-Chicco/dp/B0085KJUNK/ref=pd_bxgy_ba_img_y
You do need an adapter for an infant seat. But I also use a product called a snuggin go that you can put in the stroller to position little babies. If I use that and recline the seat, I don't need to mess with the adapter (my little one is 3 months now). That makes it fold more easily too. Plus you can use the snuggin go as a positioner in the carseat to help them from slouching to the side. If I were to do it again I would have forgot the adapter and just bought the snuggin go. Hope that helps!
Just this summer, an adapter was released for Graco car seats. It was easy to install, and worked great. I purchased it at BuyBuy Baby and it retailed for $49.99 before the 20% coupon. Hope this helps!
You will need to buy the adapter for the car seat. I didn't buy 1 because my 6 month old suits just fine and since it lays almost completely flat I wasn't worried about her being in it. It also has a huge window so it's easy to see baby even when laying flat.
It does NOT take infant car seats - I have no idea if an adapter would work - we are past that stage, and they didn't have them (that I know of) back when we needed them. I would contact Joovy directly thru email on their website - they answer fairly quickly as far as companies go - they would be the ones to answer that, or that info might even be on their actual website.
I'm not aware that you can use Infant seats with it. When looking at this and the BOB at the store, the sales clerk said the sole reason more people tend to buy the BOB is that they need to fit an infant seat in it. I didn't use this stroller until my daughter had excellent head control and I felt comfortable sitting her in a reclined position about 4 months.