On 1 May 2004 , it became a full - fledged member of the European Union , and a member of the Schengen Agreement on 21 December 2007 .
Since 29 March 2004 , Lithuania has been part of the NATO .
On 1 May 2004 , Lithuania became a full - fledged member of the European Union , and a member of the Schengen Agreement on 21 December 2007 .
Since 29 March 2004 , Lithuania has been part of the NATO .