Out of the box, its stereo, as is the case for most headsets.
Essentially, surround sound (useful mostly for FPS gaming in my opinion) is obtainable via 4 possibilities for headsets:
(1) "True" surround sound headsets (with multiple drivers in each earcup). (There are a very small number of these products in the marketplace. Personally, I'm not that keen on them, although some folks like them a lot. Examples are the Roccat Kave [5.1] and the Razer Tiamat [5.1 or 7.1].)
or
(2) Headsets with virtualisation technology built-in to their design (e.g., Corsair Vengeance 1500, Corsair Vengeance 2000).
or
(3) Stereo headsets sold with an optional virtual surround in-line "dongle" (e.g., Sennheiser PC333D, Sennheiser PC363D, ASUS Orion Pro, ASUS Vulcan Pro). (This is more elegant than (2) in my opinion.)
or
(4) Any good quality stereo headset (or headphones) connected to a soundcard that offers virtual surround sound capabilities (e.g., at time of writing: SBX Surround on the Creative SoundBlaster Z cards, Dolby Headphone for many of the ASUS cards).
The Sennheiser PC360 is category (4).