This article describes the first part of the Sankt Florian Psalter, dated in the history of art at the end of the fourteenth century. The floral borders and colouring of the manuscript make a distant reference to the Czech and Silesian illuminations from the end of the fourteenth century. The artistic level, both in terms of the style and technique of the illuminator, is amateurish and differs from the manuscripts illuminated at that area, as well as from the few examples of illuminations in Krakow. However, because of the picture, which are astrological images that were widespread in Europe, the Psalter is a unique work in Poland. The coat of arms of the Hungarian Anjou (fol. 50v, 53v), the letters mm, and the crest on the fol. 53v (the Polish eagle with a horseshoe in its beak) clearly link this manuscript with queen Jadwiga, wife of Wladyslaw Jagiello. Work on the Psalter was abruptly halted due to the unexpected death of the young queen on July 17, 1399, and was completed for another owner. The principal maker of the Psalter, who transcribed the text, authored the large and small initials, picture and figural fillings between the lines, was probably Bartlomiej from Jaslo, who also copied liturgical books for the queen. Another maker working for the queen was a miniaturist named Peter, who painted the figures of angels holding the coats of arms, the coats of arms alone, and the letters mm. The Sankt Florian Psalter is one of the many pious undertakings of queen Jadwiga, whose personality was shaped by the devotio moderna trend, based on combining vita activa et contemplativa. The letters mm, which occur on the monuments of queen Jadwiga's foundation, served a mnemonic and apotropaic function - as did the letters of different alphabets in the Middle Ages. They encoded the queen's life motto (2 Timothy 2,16 and 3,12, John 15,20, Phil 3,20), and could also serve as a talisman, necessitated by the infertility of the queen.