The subject of study of this thesis is the building lease agreement. It is an agreement that has certain similarities to other legal institutes, starting from superficies from the Roman law to the right to build, known to numerous contemporary legal systems. The specificity of the building lease agreement as opposed to other types of lease is reflected on the leasing subject – building land, whose regular use yields a new property – a construction project (facility). Given that the land and the facility constructed on it are owned by different parties, the generally accepted principle of superficies solo cedit, originating from the Roman law is abandoned. The fact that the owners of the land and the facility constructed are different opens numerous disputable questions to which the law does not provide an answer. Part of them are: what is the legal ownership outcome of the facility in case the land lease agreement is terminated? Is it feasible to establish a mortgage separately on the land and on the facility, given that they are owned by different parties and how would activating a single mortgage affect the rights of the owner of the other property? What would be the rights of the facility owner as opposed to the land owner in case of an expropriation of either the land or the facility? Numerous other questions arise.Taking into account that the majority of building land in Serbia in the second half of the 20th century was socially-owned, the specifics of the ownership form as well as authorizations arising from it that differed from the authorizations claimed by the holder of the present-day ownership forms (public, private, cooperative), a special part of the study was dedicated to the possibilities of leasing socially-owned building land, analyzing conditions under which it was possible, the purpose for which the land could have been leased, subjects that could have acted as the lease holder and the landlord, as well as the similarities and differences between leasing and the right of use.The rules on building lease in Serbian legal system are different depending on whether the land is in private, public or cooperative ownership. Only the building lease of publicly-owned land is regulated by law in more detail by provisions in the Planning and Building Act (“Official Gazette of the Republic of Serbia” no. 72/09, 81/09, 64/10, 24/11, 121/12, 42/13, 50/13, 98/13, 132/14, 145/14, 83/18, 31/19, 37/19, 9/20 and 52/21) whereas provisions in the Law of Obligations (“Official Gazette of the Socialist Federal Republic of Yugoslavia” no. 29/78, 39/85, 45/89, 57/89, “Official Gazette of the Federal Republic of Yugoslavia” no. 31/93, бр. 22/99 and 44/99) apply to all questions not regulated by the Act as well as to questions of leasing any other property. The procedure and the method of selection of the lease holder and the content of the lease agreement are regulated in detail by the Planning and Building Act as well as cases where publicly-owned building land may be leased. However, the Act is vague in terms of numerous questions such as the relation between the building lease agreement of the publicly-owned land and the agreement on public and private partnership or concession agreements for which execution the land is leased. Moreover, it is unclear about legal nature of the building lease agreement of publicly-owned land without the lease holder being obliged to pay for the lease as well as which rules from the Law of Obligations (either rules on lease or service) shall be applied in a subsidiary way. It has been pointed out to the specifics of a lease agreement that contains a provision under which the lease holder may obtain ownership of the land. A review is made within the study on certain special cases of land leasing such as the case of restitution procedure or the procedure of converting the right of use of the building land into the right of ownership for a fee. On the other hand, privately-owned and cooperatively-owned land leasing is not specially regulated by any specific act and therefore, questions related to conclusions, contents, legal fact and termination of such agreements are settled only by the provisions of the Law of Obligations on lease agreements. It is not surprising at any rate since cases of building lease in the stated forms of ownership are rare in practice, especially for project construction. However, given that Serbian law also leaves the possibility of concluding such agreements, in parallel with the analysis of the building lease rules of publicly-owned land, there is an overview of solutions that should be applied when leased land is privately or cooperatively-owned. The study shows more than 50 examples from case law that best illustrate which problems occur in legal transactions due to the existence of legal gaps in this matter and solutions on how to act in the stated unregulated situations have been proposed.