In this paper, model-based (surface, dihedral and volume scattering) target decomposition technique is proposed to decompose the π/4 mode compact polarimetric radar data. A general relationship between fully polarimetric coherence matrix and the Stokes vector of the π/4 mode compact polarimetric data is first established. Based on the Stokes vector, a proposed algorithm to retrieve the power of three scattering mechanisms is given in details. We validate this algorithm with L-band AIRSAR, San Francisco Bay, and results of decomposition are discussed and assessed in detail by being compared with the quad-pol Freeman-Durden decomposition results. Finally, the π/4 mode decomposition is compared with the CTLR (circular transmitting and linear reeving) mode, and with the π/4 mode m − δ targets decomposition. The comparison results are analyzed and discussed in detail. Keywords π/4 mode compact polarimetry, mode-based target decomposition, Stokes vector, RVoG model, radar polarimetry Citation Guo S L, Li Y, Hong W, et al. Model-based target decomposition with the π/4 mode compact polarimetry data.