Greece is a Member-State of the European Union and has ratified the Schengen Agreement. Citizens traveling inside the E.U. just need to display their police I.D. Card without the need of a passport. However, a passport is necessary for a number of other transactions, such as currency exchange, purchases, etc.
Visas are not required by citizens of Member-States of the Schengen Agreement. Greece follows the provisions of the Schengen Agreement, which abolished controls on common internal lands, at air and sea borders and allows Member-State citizens to travel around without a visa for a short stay period of up to three (3) months. However, airlines and other carriers require a valid passport and/or police I.D. Card or other form of official identification means.
Citizens of the majority of the countries that are not Member-States of the Schengen Agreement require a visa to enter Greece and the E.U. Visitors from these countries can obtain further information from the Hellenic Embassies or Consulates in their countries, or even from their travel agencies.
Visas are not required by holders of valid passports from the following non-E.U. countries if they want to visit Greece and remain in the country for up to 3 months (90 days) within a chronological period of 6 months:
Andorra, Argentina, Australia, Brazil, Brunei, Canada, Chile, Costa Rica, Croatia, El Salvador, Guatemala, Honduras, Israel, Japan, Malaysia, Mexico, Monaco, New Zealand, Vatican, Nicaragua, Panama, Paraguay, Saint Marino, Singapore, South Korea, USA, Uruguay, Venezuela
Note: During their stay in Greece, visitors with a visa must also have suitable insurance coverage for emergency medical or other needs.
(source: www.eot.gr )