This study deals with a numerical and experimental investigation of a microwave heating process in frozen and defrosted zones. The microwave power generation is computed either from Maxwell's equations or Lambert's law. For the two different approaches, a finite element method is used to design a 2D heat transfer model. The heat source term depends on the dielectric properties which are temperature dependent. Temperature profiles obtained with both approaches are compared to experiments carried out in a microwave rectangular wave guide in fundamental TE1.0 mode at 2450 MHz. Reverse technique is used to estimate dielectric properties in frozen phase and gives appreciable results when comparing numerical computation to experimental data. Resonance phenomena are observed experimentally in the frozen product and can only be predicted using Maxwell's equations. However, good agreement is found between Maxwell's equations, Lambert's law and experimental data in defrosted phase. Based on the comparisons between the experiments and the numerical counterpart, recommendations can be drawn for the microwave heating process modelling. (C) 2007 Elsevier B.V. All rights reserved.