http://blogs.insideline.com/roadtests/assets_c/2012/12/three%20across-thumb-717x538-129711.jpg

Note: The 2013 Cadillac ATS seats three in the rear.
Note: If you have three 6+ footers (6'2", 6'3", 6' when standing up really straight) they will not have enough headroom to allow circulation to their brains, nor will they have enough hip room to prevent uncomfortable levels of touching. Shoulder room is similarly lacking, it's best to sit slightly staggered.
Note: Good legroom for the guys on the outside. (Thanks for taking another one for the team, Schmidt.)
Mike Magrath, Features Editor

http://blogs.insideline.com/roadtests/2012/12/2013-cadillac-ats-three-across.html

The non-sunroof feature has plenty of headroom. Not so much for the hips....

Oh well it's a small car, whatd ya expect!