Yes, it depends on the item. It isn't the fact that it is shipped from the US that causes the duty, it is where it is manufactured. If it was both made and then shipped from the US, there should be no duty. But not everything being shipped from here was manufactured here.

http://canadaonline.about.com/cs/cus...shipcanada.htm

My family has had to pay taxes (I assume it was taxes) on things I've sent them, until I finally learned that if I value it at $20 or less then they are fine. Once I sent 2 T-shirts, that I paid probably 20 each for, and like an idiot put that on the forms. I think my cousins paid another 20 just to get the dang things.