After the First World War, the Academy was renamed 'the Polish Academy of Arts and Sciences' (PAU), and become the official representative - though not state-affiliated - of Polish learning, a status which entailed participation in international learned organizations; among other things, the PAU was a founding member of the Union Académique Internationale (UAI) . The period between the world wars was the period of greatest activity at the PAU, especially in the sphere of publications: over 100 publication series were then in print, among them the monumental Polski S³ownik Biograficzny [Polish Biographical Dictionary].
The Scientific Station in Rome was also founded during this period.

After the German Occupation, the PAU continued its activities in the same fields until 1952, when the authorities decided to take over its agencies and assets on behalf of the Polish Academy of Sciences in Warsaw, which was then being established.
The PAU was never formally dissolved, however, so that it was able to resume its activities immediately after the systemic transformations of 1989.

The process of renewing the PAU's structures and agencies began at once. To begin with, the Classes were recinstituted. Since the members of the Cracow Branch of the Polish Academy of Sciences had been automatically appointed as members of the PAU, it was necessary to divide the existing Class of Mathematics and Natural Sciences.
As a result, the PAU as of May 1990 had five Classes:
Class I: Philology;
Class II: History and Philosophy;
Class III: Mathematics, Physics, and Chemistry;
Class IV: Natural Sciences;
and
Class V: Medicine.
A sixth Class, Creative Arts, was added in March of 1993.

The PAU's publication activities were also reactivated in 1990, beginning with the PAU Annual and the Reports on Activities and Meetings, followed by the publication series entitled Papers. Successively, in a 'grass roots' manner when the perceived need coincided with the possibilities, Commissions began to be formed within the Classes, beginning with the Commission on Central Europe. There are presently 27 Commissions within the structure of the PAU.

As of 21st June, 2008, the PAU had 477 members, including 297 resident members (146 regular members, 151 corresponding members), and 178 international members, each of whom maintains active contacts with Polish science and learning. As the PAU's honorary members Pope John Paul II,
Jan Nowak-Jeziorañski, W³adys³aw Bartoszewski and Franciszek Cardinal Macharski have been elected.

Stanislaw August Poniatowski - the last King and Grand Duke of the Polish-Lithuanian Commonwealth (1764-95)