The relationship between the pore structure and the dielectric properties of cement paste is studied in this work. Dielectric properties clearly reflect the pore structure development and the degree of pore occupancy by electrolyte. Impedance spectroscopy (IS) measurements in the high frequency range (10 kHz-15 MHz) have been performed in samples with varying pore occupancy. For cement pastes with a fully developed pore structure (curing time > 28 days), when all pore families are filled with electrolyte, the main characteristic factor is the asymmetry observed in Cole-Cole plots, whereas as these samples are dried off or the pore structure is not fully developed (curing time < 15 days), the asymmetrical dispersion decreases and the symmetrical dispersion becomes more important. The relationship between Cole-Cole plots dispersions and pore size distribution in samples is shown by performing bi-dimensional simulations. (c) 2005 Elsevier Ltd. All rights reserved.