The article presents the content of private letters from the nuncio to Poland, G. Piazza, residing in Troppau, to the vicar apostolic in the north (for the area of northern Germany), Bishop A. Steffani, in the years 1706-1708. The letters show the difficult circumstances in which Piazza had to fulfill his duties as nuncio after the abdication of King Augustus II. In accordance with the point of view of papal diplomacy, he supported Augustus' right - as a legal ruler - to the Polish throne. These private letters add many details to the information contained in Piazza's official reports to the Secretary of State.