This chapter presents and analyses the philosophical views on mathematics and logic formulated by representatives of the Lvov-Warsaw School of Philosophy, in particular the scientists belonging to the so-called Warsaw School of Logic. The discussed figures include: Kazimierz Twardowski, Jan Łukasiewicz, Stanisław Leśniewski, Kazimierz Ajdukiewicz and Tadeusz Kotarbiński as well as Alfred Tarski and Maria Kokoszyńska. We have also added Zygmunt Zawirski, who worked in Lvov, Poznań and Cracow but all the time he was connected with the Lvov-Warsaw School (cf. Introduction). We will also consider the ideas of two other scientists, who have usually been recognised as the second generation of the Lvov-Warsaw School, namely Andrzej Mostowski and Henryk Mehlberg. Moreover, we will present the views on logic and mathematics held by the members of the so-called Cracow Circle: Fr Józef (Innocenty) Bocheński, Jan Drewnowski and Rev. Jan Salamucha.