You will find the car hire companies at Barcelona airport in both Terminal 1 and 2. The Car hire company in Terminal 2 is only in building T2B. Each of these companies is right next door to each other so you can be sure of cheap car rental prices.
You can try arranging your car rental directly with the companies but often internet based reservation services can give you a better price as they have negotiated discounts for bulk reservations.
Tel: +34 90 201 1959
Tel: +34 90 210 8495
Tel: +34 90 210 0101
Tel: +34 91 150 5000 (T1 and T2)
In-depth information page on Barcelona Airport Car Rental services
Location of the nearest petrol station to Barcelona Airport