This study compared displacement demands obtained from linear and nonlinear time history analyses of 2D and 3D models to investigate how 2D models reflect 3-D models. Estimates of 2D and 3D linear and 2D nonlinear models were also compared to that of 3D nonlinear model to visualize success of linear and 2D nonlinear models in seismic displacement estimates of RC buildings. A total of 288 dynamic analyses were performed with 12 different records taking into account two principal directions of 10-, 15- and 20-storey buildings. Outcomes of the current study imply that 2D representation of 3D models needs careful modelling. Buildings are usually designed according to related earthquake code considering both gravity and seismic loads. Then, an interior frame is used for 2D modelling. The periods of 3D and 2D models need to be closer for proper representation. Another observation is that the 2D linear elastic models do not properly represent the 3D nonlinear models. Thus, it is recommended to use 3D models when linear modelling is preferred. Since 2D nonlinear models represent reasonably well their 3D nonlinear ones, 2D modelling can be preferred for buildings with no irregularity due to extensive labor and time required for 3D nonlinear models.