Almost five years after Lithuania adopted the euro, some 428 million litas were kept as souvenirs or simply ignored, according to the Bank of Lithuania.
These are mostly low-denomination coins, according to Vitas Vasiliauskas, the central bank governor.
"Most of these are one, two and five-centas coins. We assume they are kept as souvenirs or simply ignored," he said at a news conference.
Coins worth 113.9 million litas and notes worth 313.6 million litas have not been returned to the central bank.
Lithuania adopted the euro on January 1, 2015. The central bank committed to exchange litas for euros free of charge indefinitely.