Lithuania is a member of the Schengen Agreement.
There are no border controls between countries that have signed and implemented this treaty - the European Union except Bulgaria, Croatia, Cyprus, Ireland, Romania and the United Kingdom, Iceland, Liechtenstein, Norway and Switzerland. Likewise, a visa granted for any Schengen member is valid in all other countries that have signed and implemented the treaty. But be careful: not all EU members have signed the Schengen treaty, and not all Schengen members are part of the European Union. This means that there may be spot customs checks but no immigration checks travelling within Schengen but to/from a non-EU country or you may have to clear immigration but not customs travelling within the EU but to/from a non-Schengen country.
Please see the article Travel in the Schengen Zone for more information about how the scheme works and what entry requirements are.
Most airlines arrive at the main Vilnius International Airport and some at the smaller, seaside Palanga Airport, while budget carriers such as Ryanair land in Kaunas International Airport. Kaunas airport also has a direct link with Riga by AirBaltic.
For destinations in Northern Lithuania, Riga Airport is an attractive option.
Major "Via Baltica" road links Kaunas to Warsaw and Riga/Tallinn. The Baltic road, which links Vilnius to Tallinn, was just reconstructed. It is a very easy and pleasant route.Overall, the major roads between the cities are of decent quality. Be extremely cautious when getting off the main roads in rural areas, as some of them may contain pot holes and general blemishes which could damage a regular car if you go too fast.While driving between cities there are usually cafes and gas stations with bathrooms and snacks.