Barcelona airport has a left luggage office, which is situated in the hall of the terminal B, beside the area of arrivals. It's a payment service and you will have to choose among three types of lockers, according to the size of the luggage which you want to leave. The prices are the following ones:
Small (34cm x 34cm x 80cm) 3,60 € day (24 horas) or fraction.
Medium (34cm x 59cm x 80cm) 4,10 € day (24 horas) or fraction.
Big (51cm x 89cm x 80cm) 4,60 € day (24 horas) or fraction.
If you need to travel with a very big or voluminous object, or you want to leave something there several weeks, there is a cheaper service: the storehouse. This service cost 1,85 €/ day, but you have to pay first the transfer from the left luggage office to the storehouse 37,08 €.
For claims on lost luggage go to Lost and Found offices. Fligthcare, Groundforce, Swissport, Newco, Iberia, Vueling and Air France have their lost and found offices in terminals A, B and C.