In the design of structural systems, it has become almost a necessity to use packaged softwares prepared according to regulations. The reason for this is that the earthquake regulations and standards, which are used for the design of the structural systems of the buildings, are quite detailed, and three-dimensional calculation models are used that more closely represent the behaviour of the structural systems under external loads. The use of packaged software in the design of structural systems provides ease of calculation to the engineer who performs the design and allows the determination of optimum cross-sectional dimensions by easily changing the system mathematical model. However, during the structural analysis carried out using the packaged software, it is very important for the accuracy of the outputs to be obtained from the mathematical model, which is formed by entering data into the software, accurately represents the structural behaviour. In this study, the issues that should be considered in the construction of the mathematical model in the structural analysis carried out using the packaged software were examined.