This paper gives a comparison of the numerical results for the induced electric field, electric current density and the magnetic flux density inside the adult, 10-year old and 5-year old homogeneous brain models, for three different transcranial magnetic stimulation (TMS) coils. The numerical results are obtained using the TMS model based on the surface integral equation (SIE) formulation. The child brain models are obtained by linearly scalling the adult brain model. The age dependent parameters of the brain are taken into account. The results showed the increased values of the TMS-evoked parameters in the smaller brain models. Further analysis is carried out to investigate to what degree the approximation of brain tissue parameters influences the results in the homogeneous brain.