Since its establishment in 1989 Croatian Democratic Union (CDU) has continuously transformed itself. It has also stood the test of time as it developed from the national movement with a sole purpose of realizing Croatian independence to the clientelistic party with a strong leader in Franjo Tuđman in the 90’s to today’s modern presidentialised right-centre party. In this thesis CDU’s transformation is analysed through three elements: party organisation, party ideology and the importance of leadership characteristics and charisma of party presidents. Organisational and ideological aspects are standard elements of the party transformation analyses, while the element of leadership characteristics and charisma of party leaders was introduced because of the specificity of CDU that regards the routinisation of Tuđman’s charisma in the organisational structure of the party itself. In the first part of the thesis a brief historical summary of CDU is provided, and then starts the analysis of the Tuđman era. In the last part of the thesis the focus is on the analysis of presidential terms of all the party’s leaders since 2000. The analysis showed that in organisational sense CDU is marked with an extremely powerful and organised inner party organisation that has a powerful party on the ground with an unquestionable role of the party president. The period post 2000 is characterised by the modernisation and presidentialization of the party with a clear tendency to present itself favourably to the majority of voters in a catch-all manner. In an ideological sense, in the 1990s CDU’s ideology mirrored the ideology of Franjo Tuđman. However, after his death CDU has started to slowly move itself towards the political centre – a process that started with Ivo Sanader and continued in the times of Jadranka Kosor and Andrej Plenković. That somewhat phased transformation had a so-called anti-wave between 2012 and 2016 during the presidency of Tomislav Karamarko when the party radicalised its rhetoric and moved itself from the moderate and centrist policies characteristic of previous party presidents.