The subject of this thesis is two types of floor structures that are used on larger spans in high-rise buildings. These are post-tensioned monolithic slabs (PT slabs) which are compared with the monolithic design of slabs without pre-tensioning. Analysed building, skyscraper B, stands out as the only one in the Skyline complex built in PT technology. The thesis emphasizes the technical and economic advantages of using prestressed slabs in comparison to non-prestressed slabs. A comparison of the prestressed slab in question with the non-prestressed variant which thickness is determined so its total deflection match those realized when using the prestressed slab. The comparison is interesting because the two neighbouring skyscrapers, built in the non-prestressed version, had larger deflections than expected. Prestressed slabs have multiple advantages, both through a reduction in the quantity and cost of materials, as well as through a faster construction due to earlier removal of the formwork. Also, with prestressed slabs spanning over 8,0 meters capitals in the column area are avoided which also simplifies and speeds up construction. So, such pre-tensioned slabs, with span over 8,0 meters, can be made with a slab of constant thickness, thinner than the non-prestressed one, and the problem of column and slab punching force is solved by including the deflection forces of the cables in the column zone, which significantly reduce the punching force. The final part of the thesis presents the applied technologies of building skyscraper B of the Skyline complex, and the conclusions of the subject analysis.