No, the smaller of your items should be under the seat in front of you.

I travel light yet have been blasted by other passengers for having my backpack in the overhead. People asking "whose backpack is this ?" then informing me I should put it under the seat (to make room for their oversized bag). I just point to my netbook case already under the seat. That usually earns me a dirty look, even though I'm the one who is travelling smart and obeying the rules.

Steve