In order to detect 2D underground heterogeneity between boreholes, a microwave-imaging technique is presented along with numerical and experimental comparisons. The proposed technique is based on a spectral diffraction tomography technique which enables heterogeneities from the polarized currents induced by the incident field of a simple dipole antenna to be located. Numerical results in both a tranverse-magnetic (TM) raid transverse-electric (TE) modes are compared with a reduced-scale physical model composed of a water tank with some immersed cylindrical heterogeneities. (C)2004 Wiley Periodicals, Inc.