Carry-on backpacks and carry-on luggage are like bourbon and whiskey. All carry-on backpacks are carry-on luggage, but not all carry-on luggage is a carry-on backpack. Carry-on luggage can take many forms, including rolling suitcases, purses, duffel bags, etc. But a carry-on backpack is always in the form of something you can carry on your back. It’s also important to note that a carry-on backpack could qualify as either a personal item or a carry-on bag, according to airline regulations.