Grand Duchy of Lithuania (GDL), as the Lithuanian State was known from the middle of the 14th to the end of the 18th century, had ancient traditions of parliamentarianism. In contrast to the centralised states of Europe, which later became absolute monarchies, the GDL remained, even after the union with Poland in 1569, a parliamentary republic. An elected monarch ruled the republic, and the state power was concentrated in the parliament (Seimas), in which only the noble estate participated.

The Seimas (parliament) has been known in the history of Lithuania since the second half of the 15th century when the representative parliament of the Grand Duchy of Lithuania (GDL) was convened by the Grand Duke. Later it was convened by the Council of Lords. Parliaments met either in Vilnius or in Brasta (the present Brest). The Seimas elected the Grand Duke, discussed the major issues of home and foreign policy, and took control of the state treasury. In the middle of the 16th century the influence of the noblemen in the Seimas began to increase: up till that time all decisions were prepared in advance by the Council of Lords and the Chancellor, in other words, by "the government" of the Grand Duchy of Lithuania.

From the beginning of the 16th century the Seimas of Lithuania started fulfilling legislative functions. On September 29, 1529, the Statute of Lithuania, prepared under the guidance of Chancellor Albertas Goštautas, was adopted by the Seimas of Vilnius. It included legal norms of the state, as well as administrative, criminal, civil and military affairs and consisted of 250 articles. From the customary law and the law of privileges granted to the estate of the nobility, Lithuania moved to a new level of a written legal system.

In the course of several centuries, after Lithuania was christened, not only interior traditional relations of Lithuania but also the concept of law in the society changed. The estate of nobility was granted the privilege of ruling the State. This was a positive achievement in reforming political life of the GDL, however, on the other hand, noblemen, being able to exert influence not only upon the Council of Lords but also on the Grand Duke, actually were not accountable to anyone. This fact could be regarded as one of the incentives for the Polish Kingdom to intensify diplomatic relations and to form a united state with Lithuania. The opposition to the initiative of Poland of such Lithuanian noblemen as Mykolas Radvila Juodasis, his cousin Radvila Rudasis or the Chodkevičiai was overcome. The integration processes prevailed when a union (The Lublin Union of 1569) with Poland took place. The Union Act did not declare a united republic but a federation of two separate states, Poland and GDL. Lithuania had its own government, separate from that of Poland, its own form of parliament, its own courts and legal system.

However, The Liublin Union (1569) formally abolished individual parliaments of the Lithuanian and Polish states, and established a single joint parliament for the entire republic, the Commonwealth of Poland and Lithuania. This was a turning-point in the history of the old influential country in the Baltic region, and restricted the independence of the country: up until the year 1653, as provided for in the Union Act, the Seimas met every two years for a six-week session in Warsaw (Poland) and, beginning with 1673, every third session met in the Grand Duchy of Lithuania; a nobleman of the GDL was elected Marshal of every third Seimas.

The structure and working procedure of the Lithuanian and Polish Seimas restricted the role and influence of the King. The most important thing was that laws were passed not by a majority of votes but only unanimously, in other words, by the principle of the liberum veto, which paralysed the work of the joint Seimas: it could be and often was interrupted by the opposition on the part of any of its member, and thus many of the sessions were dissolved.

In a sense, the noblemen tried to "preserve" the Seimas of the Grand Duchy of Lithuania till the 17th century by convening individual sessions to discuss the policy of the GDL and the position of its representatives prior to the sessions of the Lithuanian and Polish Seimas. Of course, it was a peculiar way of slowing down the process of merging the nobility of the two nations, as well as that of restricting the independence of the GDL, all the more so, that Lithuania preserved its state treasury and the army.

However, absence of a strong centralised power weakened the foreign policy: after The Lublin Union of 1569, Lithuania's neighbours - Prussia and Russia - became strong politically and military. Traditionally, Russia further recognised the power of the Grand Duchy of Lithuania, thus, the whole Republic was valued according to the image that the GDL had formed.

However, the GDL, as a part of the Commonwealth of Poland and Lithuania, was unable to pursue a consistent policy with respect to Prussia and Russia. The GDL, upon losing the independence of power institutions, being torn by disagreements among the nobility, surrounded by strong neighbours, first lost its statehood in the republic, and at the end of the 18th century, together with Poland, experienced a grave political crisis. Noblemen pursued a policy of pacifism: they falsely hoped that the State's border security could be guaranteed by the old treaties with Prussia and Russia. On May 3, 1791, at the demand of the citizenry of Warsaw, the Parliament adopted the Constitution of the Republic. The Constitution was the last will and testament of the dying Republic. In 1795 the Republic was divided between Russia, Prussia and Austria.

From 1795 to 1918 the public life in Lithuania could not develop normally due to the lack of statehood. Lithuania promulgated independence on February 16, 1918, following 123 years of captivity, and the Constituent Assembly (Seimas), the first democratically elected parliament, convened for its first sitting on May 15, 1920.