The society's board chairman Algirdas Vaicekauskas told BNS that a report for the past four years would be presented at the congress, which will elect a new leadership and discuss further fields of activities.
Poland's Lithuanians also intend to discuss the problems in connection to insufficient funding of education and heritage preservation.
"Problem-solving is a process, which, unfortunately, is very sluggish," Vaicekauskas said.
Vaicekauskas, principal of Žiburio school in Sejny, noted that the school would not be able to operate without financial assistance from Lithuania.
Poland's Lithuanian society was established in 1957.
"This is the first Lithuanian organization founded after the war, during the political thaw and amid Poland's recognition of existence of national minorities. Immediately after the war, every effort was made to make Poland homogenous in terms of national minorities," he added.
Poland's Lithuanians sent an open letter to Lithuanian and Polish prime ministers last November, warning of the increasingly worsening situation of the Lithuanian community in Poland.
According to the document, the network of Lithuanian-language schools is being narrowed, primary needs of providing schools with textbooks are ignored, students studying all subjects in the Lithuanian language are subjected to financial discrimination in respect of the students who only attend classes of the Lithuanian language.
The community also recalled vandalization of bilingual signs in Punsk municipality along with two monuments to Lithuanian cultural figures, with culprits still unidentified.
According to data provided by Lithuania's Embassy to Poland, about 15,000 people of Lithuanian origin currently reside in Poland, mainly in Sejny and Punsk regions close to the Lithuanian border.