Non-destructive techniques are the future of structure health assessment and monitoring. The dielectric permittivity is sensitive to the water and ionic content of concrete and it can be measured by capacitive probes. In this paper, an inversion method to obtain the permittivity profile inside reinforced concrete from surface capacitive measurements is presented. The inversion process is applied to synthetic models using two forms of parametrizations (discrete and continuous). In addition, the effect of data noise on the inversion is studied. At last, water saturation profiles inside a concrete slab are obtained by means of inversion of experimental capacitive data.