Things can get steamy when it comes the erotic massage scene in Porto. It might not be huge but the quality is very respectable. Studios like the Diva Spa (http://www.divaspa.pt/) at Rua Simão Bolívar and Glamour Spa (http://www.spa-porto.pt/) at Av. da Boavista flaunt their gorgeous girls on their websites and offer interesting packages of massagem erotica or massagem sensual.
There are only a handful of studios in Porto, but you for more options you can give it a try with escort agencies, which might have escorts with decent massage skills in her stable. Portuguese directory sites and classifieds, where individual masseuses (massagistas) offer their services, are also worth checking out. Expect to pay at least €100 for a 1 hour session.