The article “Legal Institutions Securing Socially Recognised Rights of the Subjects Participating in Legal Transactions, Based on the Example of Legitimate Expectative” sheds light on the concept of legitimate expectative as a separate right. It gives arguments in favor of qualifying this type of right as legitimate since it protects legally important issues connected with the transactions undertaken by the participants of the market. The article also draws attention to the decisions of the international tribunals and the European legislatives that grant the position of the legitimate expectative in the general system of law. Coined by the German doctrine of law under the names: Anwartschaft, Wartenrecht and Zwischenrecht, the notion of expectative becomes widely recognised in other European countries, also in Poland, which is highlighted in the text. The protection of the said right in the Polish law system is mainly guaranteed by the Polish Constitutional Tribunal, in the described in the article decisions of 1989, 1993 and 1996. The topic of the article is not only the analysis of the said right of expectative but it also aims at a more general issue which is the creation of the new rights in JOANNA BOCIANOWSKA 191 very traditional civil law systems, especially in the Polish one. The summary of the analysis shown in the article leads to the conclusion that new rights and regulations are necessary, and the source of them should stem from the needs of the society, not the needs of the state.