You may also buy the combined tickets:
•Full festival ticket for both Optimus Primavera Sound 2013 (Porto) + Primavera Sound 2013 (Barcelona): 200.00€.
•Full festival ticket for both Optimus Primavera Sound 2013 (Porto) + Primavera Club 2012 (Barcelona or Madrid): 120.00€ - available from October.
You can buy them at Ticketline, Ticketmaster, Paypal, Seetickets UK and Ticketscript. Distribution costs are not comprised in the ticket price.
Follow the news at http://optimusprimaverasound.com/
Source: VisitPorto.travel website