A lease agreement is a bilaterally binding contract in which the lessor undertakes to hand over a thing to the lessee for use, and the lessee undertakes to pay them a certain rent for that. The topic of this thesis is the Apartment Lease Agreement, which is a special form of lease and as such is regulated by the Apartment Lease Act. In addition to the Lease Act, the Civil Obligations Act as a general law also applies to the lease agreement. This thesis is divided into three parts in order to better present and explain the topic. The first part discusses the history of lease agreements in general. The second part of the paper explains the lease agreement and elaborates the terms lessor and lessee, rights and obligations of the lessor and lessee, concluding a lease agreement, fulfilling the lease agreement and termination of the lease agreement. The third part of the paper is dedicated to the institute of protected tenants. This part of the paper explains the concept of protected tenant, its origin, but also the right of occupancy that preceded the institute of protected tenant. The Apartment Lease Act 1996 is also mentioned, which introduced the institute of protected tenant. In order to better present the topic, two decisions of the Constitutional Court of the Republic of Croatia and the judgment of the European Court of Human Rights are also mentioned. The Croatian legislature has been trying to solve the institute of protected tenant for thirty years, but without success. It has failed to find a solution to a number of problems that have arisen with regard to protected tenants.