The aim of this study is the comparison of the 2D and 3D finite element time-dependent analysis for interstitial microwave hyperthermia treatment. The described method is based on microwave heating of pathologic human tissue using a thin coaxial-slot antenna placed invasively in the diseased tissue. The shown problem relies on the solving of coupled electromagnetic and thermal fields under the assumption of an axial symmetrical model. The wave equation in a sinusoidal steady state and the bioheat equation under a transient state condition are considered. The numerical calculations for the 2D and 3D models give consistent results with an acceptable level of relative error. Increasing the finite element mesh density for the refined 2D* model leads to a more accurate evaluation of the tissue temperature while reducing computation time.