I used to carry Zoey in a regular Sling backpack. It's not a very good picture but I think you get the idea..
I now use a doggie backpack and you can see the picture here:
http://www.yorkietalk.com/forums/my-...-backpack.html
Zoey likes both but I made the switch because the sling was starting to really hurt my shoulder. If you're planning on using it just occasionally, the sling might not be a problem but if you're like me and carry her every day for our walks, you might consider the 2nd backpack.