thank you for your reply.
Yes, that method works fine.
However, in some situations, I need to get the weight of each item in the cart.
However, I was inspecting its implementation: it takes the quantity into account only if the ShoppingCatrItem object has some AttributesXml, which I don't know where they should be coming from...
Anyways, I'm fixis this by multiplying the returned weight by the item quantity myself... even though I don't understand why the services doesn't do this on first place...