The chromatographic performance with respect to the flow behavior and dispersion in fixed beds of nonporous and macroporous particles (having mean intraparticle pore diameters of 41, 105, and 232 nm) has been studied in capillary HPLC and electrochromatography. The existence of substantial electroosmotic intraparticle pore flow (perfusive electroosmosis) in columns packed with the macroporous particles was found to reduce stagnant mobile mass transfer resistance and decrease the global flow inhomogeneity over the column cross-section, leading to a significant improvement in column efficiency compared to capillary HPLC. The effect of electroosmotic perfusion on axial dispersion was shown to be sensitive to the mobile phase ionic strength and mean intraparticle pore diameter, thus, on an electrical double layer interaction within the particles. Complementary and consistent results were observed for the average electroosmotic flow through packed capillaries. It was found to depend on particle porosity and distinct contributions to the electrical double layer behavior within and between particles. Based on these data an optimum chromatographic performance in view of speed and efficiency can be achieved by straightforward adjustment of the electrolyte concentration and characteristic intraparticle pore size.