Only if it fits through the little scanner. If you took a soft duffle, it would fit because length doesn't matter. But remember, if your room isn't ready when you board, you will be schlepping it all around the ship with you.
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Judy
Celebration 2/96
Imagination 2/97
Fascination 12/97
Imagination 3/99
Spirit 11/01
Sensation 1/02
Pride 11/02
Voyager of the Seas 5/03
Conquest 10/04
Conquest 10/29/06
Inspiration 11/08
Celebrity Solstice 2/09
Oasis of the Seas 10/16/10
Usually the cabins aren't ready until around 1:00, so you have to already carry your carry-on with you until then. Just turn over the regular luggage to the porters when you arrive at the pier, tip them a few dollars and it will show up in your cabin in a few hours.