The purpose of this thesis is to show the method of rent assessment for the instalment of optical cables into a public ligthing duct system when the owner of such a duct system is the local community and the future lessee is the administrator of a communications network. First the elementary characteristics of construction and usage of communications networks and public lighting networks will be shown, the emphasis on the specificities of communications networks. Next, we will show how to assesse the value of rent for the purpose of a public ligthing duct system lease, using the methodology of rent assesment for the instalment of optical cables into a public ligthing duct system. The value of the average cost of construction of a public lighting duct system in the City Municipality of Kranj is calculated on the basis of the cost of construction of a duct system and the value of land. The initial value of annual rent is estimated by using the method of direct capitalization. The usage of adjustment factors for the rent assessment of specific, concrete examples is described next. In the last chapter rent assessments of specific cases of the instalment of optical cables into a public ligthing duct system in various locations in the City Municipality of Kranj are presented. The evaluation of the adequacy of assessed rents follows. In the closing arguments we recommend that before a duct system is leased, records of free capacities and a plan of development of the public lighting network are made.