Before the century period underlined in this article, the Catholic presence in Moldavia was concretized in the existence of the Milcov and Cumanian (1227-1241) bishopries, wanted by the Hungarian crown, and afterwards, in the ones of Siret (1371-1434), Baia (1418-1525) and Bacău (1607-1818), constituted in the context of the Polish crown’s Catholic interests. For the Bacău bishoprie, the De Propaganda Fide Congregation nominated the Minor Conventual Franciscan Order with the purpose of watching over the destiny of the Catholics in Moldavia. Until the XVIIIth century, the conventuals had great difficulties in Moldavia, conquered by the Ottoman empire and devastated by various wars and pillages, and this missionaries had to watch over „the Catholic flock”, the Catholic minority that, by 1600, numbered about 300 souls. At the end of the XVIIIth century, the number of Catholics rose up to 13,000. The article presents the extreme conditions of the Catholic mission in Modavia, stoping upon some facts, institutions and persons that influenced the development of the mission. Thus, the authority of the Bacău bishops is underlined, and the main discussion is upon the protectorate of the big European powers – as Polland, Russia and Austria –, upon the missionaries’s relations with the local authorities – the rulers, the boyards and the Orthodox clergy – ; the controversies among the minor conventual franciscans aren’t much underlined.