Sometimes. Because in English we write from left to right, a lefty is often found to push the pen or pencil into the page, whereas a rightie simply moves the pen or pencil and draws the lead or ink out. The rightie has the advantage there.
Also, dragging one's hand across the page is an issue for a leftie. To avoid it, a child may find him or herself writing with a hook or claw hand, which requires a different grip, as well. This positioning limits hand movement and can tire the hand and arm muscles.
My leftie daughter needed direct instruction on how to position herself and her pen. We got a great resource from an occupational therapist family friend:
http://www.youtube.com/watch?v=5Ql8-L5i_j0
From this resource
http://www.anythinglefthanded.co.uk/ we bought what looks like a placemat that shows right and left handed positioning of paper, as well as some handwriting books (that demonstrate how to cross t's from right to left, which is a more natural movement for a L-tie) and some pencil grips that position the fingers naturally in a pincer type grip.