Reconstructions of two dimensional dielectric or conducting objects from multi-frequency experimental data are considered in the present paper. Two different iterative methods are used for solving the inverse scattering problem. The first one is based on a boundary integral formalism and retrieves boundaries and complex permittivities of unknown homogeneous scatterers. For this method initial guesses are derived from method of decomposition of the time reversal operator (DORT) combined with a low frequency approximation. The second method is based on a domain integral formalism and retrieves the relative complex permittivity distribution inside some investigated domain. The data were carried out in a controlled environment (anechoic chamber) and the reconstructions have been performed using multifrequency approach, i.e., the scheme starts with the lowest available frequency and uses the final result as initial guess at higher frequency in order to enhance the resolution.