I guess they are, but my Pasela tires are listed as "23c" or "28c" width so I guess I tend to read it as cm's which is probably incorrect. Surely they mean mm in any case!
Just jumping back a page or two...
Yup... a bit of research (talking with other cyclists and measuring tyres)... of course it is mm... why they say "c" instead of "mm" though, I have no idea...