In my paper, I analyse testimonies from the period of the first Piast monarchy indicating the importance for Polish rulers of contacts with the Holy See, combined with selected testimonies of the significance of the cult of St Peter the Apostle (the first Bishop of Rome) for the Piasts. I compare the cited testimonies to the actions taken towards the Holy See by the Slavic rulers (including the Croatian prince Branimir and the Great Moravian prince Svatopluk) and the Bulgarian khan Boris from the 9th century, who devoted themselves ‘in servitio beati Petri’, which, in my opinion, was supposed to justify the involvement of the Holy See in the creation of an ecclesiastical organisation in their subordinate area. In comparison to this model of behaviour, I try to determine what purpose the contacts of the first Piasts (Mieszko I and later Bolesław the Brave) with the papacy served and to what extent they could relate to the actions of the ninth-century rulers.
