I really like these pants for bed.  They are comfortable and a thin light fabric.  They look good too.  Just like everyone else's review, the pants are a little long for the legs.  It's not really a problem because you can just pull them up a little higher or you can roll the waist band several times.

I have about a 35 inch waist and ordered a large.  They fit comfortably and stay up just fine.  I think the measurements recommended a medium but I went larger because I didn't want it to be too tight around the waist.  I probably would stick with a large if I was a 33 or 34 inch waist.  That may just be me though.