Within the European Union’s borders, visas are not required.
Citizens of the following countries can travel to Poland without a visa:
Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Monaco, the Netherlands, Norway, Portugal, Romania, San Marino, Slovakia, Slovenia, Spain, Sweden, Switzerland, the United Kingdom. Visas are required for citizens of Russia, Belarus and Ukraine.
Since December of 2007, Poland has been a member of the Schengen Agreement. For the whole territory of the Schengen Agreement, there is no passport control at the borders. Anyway, it’s always required to carry ID when travelling abroad.
These are the countries of the Schengen Zone:
Austria, Belgium, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, Malta, Monaco, the Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden.
Two members of the EU are not members of the Schengen Agreement: Great Britain and Ireland.