In reply to FrankBooth:
Ryanair now allow two pieces of hand luggage (one big, one small), so I expect it'd fit as the second.
Just in case you want to check:
One cabin bag weighing up to 10 kg with maximum dimensions of 55cm x 40cm x 20cm, plus 1 small bag up to 35 x 20 x 20 cms may be carried per passenger*.
www.ryanair.com/en/terms-and-conditions/regulations-cabinbaggage/
Note though that a duty free bag also counts as item number 2, you aren't allowed that as well.
Neil
Post edited at 23:23