The post of president of the European Commission has been and still remains one of the most important in the structure of functions within the whole European Union. From the formal point of view the EC head is placed after the president of the European Council. However, due to the practical prerogatives assigned to him in treaties, they are often treated as the first and most important person. Hence, the elections of the president of the Commission were usually accompanied by political emotions. In the years 2004-2019 the largest extension of European Communities took place but at the same time some basic legal acts were rejected and the new ones were adopted. Although their provisions, which determined the procedure for electing the president of EC and which extended the latter’s competences, did not in principle undergo any greater modifications, their legal interpretation was definitely changed. The main axis of dispute was the European Parliament taking over the prerogative of appointing a candidate for the head of EC, till then belonging to the European Council.