The aim of the paper is to present and discuss the main views and tendencies in the philosophy of mathematics of the members of the Lvov-Warsaw Philosophical School and of the Polish Mathematical School, and to assess the influence of these views on logic and mathematics. One should start by stressing, on the one hand, the fact that logicians and mathematicians in Warsaw in the interwar period closely collaborated and mutually influenced each other and, on the other, that Warsaw mathematicians were interested in philosophical problems concerning mathematics and, vice versa, philosophers and logicians were open to mathematics and its philosophical problems.