Parliament leader Vytautas Landsbergis predicted victory Saturday for a referendum on creating an American-style presidency in the former Soviet republic.
Landsbergis - the likely front-runner for president if the vote passes - presented the plebiscite as a test of his government's popularity and to increase pressure for the withdrawal of at least 35,000 former Soviet troops.
But his critics worry that a presidency without checks and balances could be dangerous for a country that won its independence just 10 months ago.
If the referendum is approved, elections could be held within four months. Landsbergis would remain leader until then.
Early results from the referendum were expected Sunday, and a final tally in two to three days.
The ITAR-Tass and Baltfax news agencies also predicted the referendum would be approved.
More than half of the country's 2.5 million eligible voters must cast ballots for the result to be binding. At least 48 percent of voters cast ballots by 4 p.m., four hours before the polls closed, said Violeta Gureckiene, an official at the government electoral commission.
The turnout was low compared to previous votes, such as the independence referendum that drew 99 percent.
In Kaunas, Lithuania's second-largest city, voting was disrupted when tear gas grenades were thrown into two voting places, said parliament spokeswoman Diva Venckus. The buildings were evacuated and voting resumed later outside. Officials said they did not know who threw the grenades or why.
Lithuania had a president until World War II, before the country was absorbed into the Soviet Union.
The president would be limited to two five-year terms. Although the president's exact powers haven't been spelled out, officials have likened the job to the U.S. presidency.
Supporters argue that Lithuania needs a strong president to overcome opposition within parliament to Landsbergis' reform plans. The standoff last week led Prime Minister Gediminas Vagnorius to submit his resignation after lawmakers prevented him from firing two top officials.
Some voters expressed hope that a popularly elected president could press Russian President Boris Yeltsin to withdraw troops from Lithuania.
Russian and commonwealth officials have said they will pull out the forces only as fast as they can find places to relocate them.
The government has scheduled a referendum on June 14 in which Lithuanians are expected to vote overwhelmingly for an immediate army pullout.