Citizens of the European Union, Bulgaria, Cyprus, Iceland, Liechtenstein, Norway, Romania and Switzerland need only an identity card to enter Portugal.
In addition to their identity card, minors must also present authorisation from their parents to travel.
For visits of less than 90 days, a passport valid for at least three months after the end of their stay is necessary for visitors from Albania, Andorra, Antigua and Barbuda, Argentina, Australia, Bahamas, Barbados, Bosnia-Herzegovina, Brazil, Brunei, Canada, Chile, Costa Rica, Croatia, Guatemala, Holy See, Honduras, Israel, Japan, Macedonia, Malaysia, Mauritius, Mexico, Monaco, Montenegro, New Zealand, Nicaragua, Panama, Paraguay, Saint Kitts and Nevis, San Marino, Serbia, Seychelles, Singapore, South Korea, United States of America, Uruguay, Venezuela, Special Administrative Regions of the People’s Republic of China in Hong Kong and Macao and Taiwan territorial Authority.
Citizens from countries not mentioned above need a visa to enter Portugal, which may be requested at the Portuguese Embassy or Consulate of their country for stays of up to 90 days.
Under the terms of the Convention Implementing the Schengen Agreement, flights between Schengen states are considered to be internal flights and passengers do not need to obtain another visa.
[ source: www.visitportugal.com]