Rotational modulation of the intensity and polarization spectra of magnetic stars offers a unique possibility to reconstruct the structure of surface magnetic fields and to investigate their relation to cool starspots. We have developed a new magnetic Doppler imaging code which aims at self-consistent temperature and magnetic mapping of cool active stars. Our magnetic imaging procedure is capable to model directly individual atomic and molecular features in all four Stokes parameters using realistic polarized radiative transfer and most up-to-date opacities, equation of state and model atmospheres of cool stars. Here we present magnetic Doppler imaging analysis of high-resolution circular polarization observations of active star II Peg. We demonstrate that self-consistent approach to magnetic mapping of this object unveils magnetic fields substantially stronger than found previously through disjoint analyses of polarization and intensity observations of active stars.