The anti-corruption organization assessed the enforcement of the OECD Anti-Bribery Convention in its member states.
"Lithuania's record in investigating foreign bribery is modest so far. Difficulties in securing effective bilateral cooperation with relevant foreign countries and institutions may potentially undermine investigations," the organization said in the report.
However, it praised Lithuania for having taken "significant steps to strengthen its legislative framework to combat foreign bribery".
Lithuania has in recent years imposed heavier penalties for corruption offenses and broadened the scope of these crimes. It has also passed a law on whistleblowers' protection, which will come into force next January.
Transparency International's experts say that there are two ongoing foreign bribery investigations in Lithuania. The country's law-enforcement officials say, however, that more international corruption probes are underway.
The Special Investigation Service (STT) is looking into allegations that an US army officer was bribed to secure a contract for a Lithuanian company.
The other investigation involves Judex, a Lithuanian frozen food company that is suspected of having tried to influence officials of the State Food and Veterinary Service to avoid being fined for violations. Law-enforcement officials suspect that the service received information from Russia that listeria bacteria had been found in Judex's products, but concealed the fact and took no action.
STT also notes that following a successful investigation, Gediminas Zumaras, the Klaipėda port's former director for infrastructure, was convicted this year for accepting a bribe from Genadijs Kamkalovs, a former chairman of the management board at Latvia's construction company Latvijas Tilti.
The anti-corruption agency also says that it is continuing its investigation into suspected corruption at the Lithuanian National Blood Center. Joana Bikulčienė, the center's director, and Antanas Petrošius, shareholder of Solis Tribus, are suspected of having attempted to monopolize blood plasma collection in Lithuania and Latvia.
According to Transparency International, no foreign bribery investigations are being conducted in Estonia.
Poland has successfully completed two foreign bribery investigations, but the country ranks lower than Lithuania because it has a larger share of global exports.
Transparency International did not assess Latvia's efforts to combat foreign bribery because of its low share in world exports.