The purpose of this paper is to answer the question of whether it is economically feasible to design and construct composite structures with lightweight aggregate concrete for the market of the Republic of Serbia. To provide an answer, a composite structure was designed (in accordance with all Eurocode standards and regulations for the design of such structures) using lightweight aggregate concrete and conventional concrete, based on a specific building example. During the design process, all parameters between the two composite structures were kept identical. After the design was completed, an analysis was conducted of the quantities of materials used (concrete, reinforcement, structural steel) as well as the unit prices of materials on the Serbian market.