Electroosmotic flow in packed capillary electrochromatography (CEC) may deviate considerably from the assumed flat velocity profile due to thermal and electrical double-layer overlap effects occurring in sections of poor permeability. It is thus highly desirable to devise a method for proper characterization of the flow permeability of packed columns used in CEC. Here we describe such a method which is based on the well-known relationships between the electrical properties and structural factors of a porous medium. The approach involves the measurement of electrical conductivity for columns with and without chromatographic packing and the calculation of relative conductivity lambda. The lambda value is then used to indicate the flow permeability of the packed column. Experiments with three well-packed capillary columns found the lambda values ranging from 0.31 to 0.34. These results appear to confirm the theoretical prediction that relative conductivity is essentially a structural constant and thus independent of column dimensions, particle size, and field strength.