The diagnostics of power transformers is very important in order to plan repairs and replacements of aged population of transformers operated in Poland and Europe. One of these methods is Frequency Response Analysis–FRA. It can detect any mechanical changes in active part of transformer, which may even lead to serious faults of units in service. As the method is based on comparison of measured curves, which are not always available from previous measurements the computer modeling was applied to create models of windings’ response. The paper presents examples of models created for simple windings and also for real transformer with some deformations of windings simulated.