Any luggage that you carry on with you must be able to fit thru the xray machine ( just like the airport). Recently there was a man that had a large roll on suitcase, that I thought would never go thru the xray, but it did. Also, a backpack is great to take on a cruise. You can really stuff it full and then you can take it when you go on excursions.
Carry on can be up to 24" wide x 16" high (thick) and any length; thats the max. dimensions of the x-ray scanner. I also pack an extra bag (the kind that folds up real small and opens to a med. size soft duffle) and I use it to pack souveniers purchased in ports; returning through the terminals they do not x-ray carry on bags....they will check your liquor allowance (duty free) for overage if carried in one of those cardboard boxes from the ship's stores. We pack our liquor packages between soft clothing in the locked luggage - no one checks those!
Think before you speak......words are not connected to a retractable cord!
"Time you enjoyed wasting, was not really wasted at all" ~ John Lennon
Carnival Victory to N/E & Canada 7 days