The diplomatic career of Roman Knoll is presented and discussed i detail from the autumn of 1921, when he fulfilled the function of the legation counsellor at the Polish Embassy in Moscow. He began his diplomatic career in 1918 as a member of the political secretariat of the Representation of the Regency Council of the Kingdom of Poland in Russia. In the following years he worked in the Eastern Department of the Ministry of Foreign Affairs and headed the Department for Russia, the Ukraine and the Caucasus. In 1921 Knoll took part in the peace negotiations in Riga. In December 1922 he began officiating as the head of the Polish legation, a function fulfilled to the end of October 1923, during a period of harsh tension in Polish-Soviet relations. Knoll was one of the advocates of a stern and unrelenting policy towards the Soviet Union, and maintained that only a decisive stand of the Polish government could persuade the Soviet authorities to implement the clauses of the Treaty of Riga. As the head of the Polish Embassy in Moscow Knoll not only was in favour of avoiding unnecessary tension, but also endorsed the establishment in Warsaw of a centre of studies about the east, thus turning Poland into an expert on Russian questions. However his idea to expand the network of Polish diplomatic and consular outposts in Russia did not meet with the total understanding of A. Skrzynski, the then head of Polish diplomacy. Despite the encountered obstacles, Knoll enjoyed considerable successes in Moscow. In contrast to his predecessors, he gained access to the whole leadership of the People's Commissariat of Foreign Affairs and maintained contacts with numerous leading Bolshevik politicians. He also developed a network of contacts among the Russian population. One of his achievements was the prolongation of the terms of the repatriation of Poles in Russia as well as inauguration of talks about a Polish-Soviet trade convention. .