In this thesis, the seismic behavior of residential buildings designed in 1964 in the city of Osijek has been observed. Expansions of three residential buildings were chosen arbitrarily, according to the criteria of quality and preservation of archival materials and the presence of vertical reinforced concrete elements. The observed buildings had been modeled as spatial reinforced concrete frame systems with masonry infill given in the form of line load. Auxiliary systems of spatial reinforced concrete frames with modeled masonry infill had also been modeled in order to investigate the influence of masonry on the seismic behavior of structures. The models had been loaded with a permanent load in accordance with a project documentation and imposed load in accordance with the current standard (HRN EN 1991-1, HRN EN 1991-3). The material and geometric linearity of construction elements was applied. The linear dynamic calculation method, i.e. response spectrum analysis was used. Structural analysis was performed using SAP2000 software. Earthquake load in the models was determined by using response spectrums from strong-motion records and response spectrums in correspondence with the currently valid standard (HRN EN 1998). Strong-motion records were used for the comparison of absolute and relative displacements. The bearing capacity of the buildings was determined by scaling the value of the peak ground acceleration as the variable of normalized response spectrum, which provides an assessment of the seismic behavior of the building and a presentation of the critical locations of the analyzed structures.