RoamTheWorldCellPhones.com

Cellphone GSM Frequencies: 900/1800

(This means you will need a GSM cellphone that will work on 900MHz or 1800Mhz to use it in Portugal.)

Cellular carriers for Portugal

Sonaecom – Serviços de Comunicações, S.A. (OPTIMUS)

Frequency: GSM 900/1800
Website: www.optimus.pt

Coverage Map (NONE)

TMN Portugal

Frequency: GSM 900/1800
Website: www.tmn.pt

Coverage Map (NONE)

Vodafone Portugal

Frequency: GSM 900/1800
Website: www.vodafone.pt

Coverage Map (NONE)

If you've used either of these networks or roamed in Portugal, please post about your experience and the cost. Feel free to ask questions.