Apart from Josipovic, in attendance will be Presidents Giorgio Napolitano of Italy, Heinz Fischer of Austria and Pal Schmitt of Hungary, the Office of Slovenian President Danilo Tuerk said on Wednesday.
The heads of state and other prominent guests will attend the central ceremony in the Kongresni Trg square in the centre of Ljubljana this evening.
The attendance of the four presidents from the neighbouring countries at the ceremony on the occasion of Slovenia's Statehood Day symbolises the respect which Slovenia enjoys in its immediate neighbourhood and in the international community and sends out a message that Slovenians can look with confidence to the future and the prospects of their country's development, reads a statement issued by President Tuerk's office.
Both Croatia and Slovenia celebrate their Statehood Day on 25 June in memory of their declaration of independence from the Socialist Federal Republic of Yugoslavia on 25 June 1991.
Addressing foreign reporters on Thursday, President Tuerk supported Croatia's joining the EU as soon as possible and the continuation of integration processes in southeastern European countries.
According to the Slovenian media, Slovenians are proud of the achievements in the last 20 years but they are concerned about the halt in the development of their country and the slow recovery from the recession, as well as about the country's growing debt and unemployment.