Results for pyridine (Py) adsorption on columnar-structured (cs) gold substrates from acid solutions at different potentials and 298 K are compared to the predictions of a recently proposed Langmuirian adsorption model at columnar surfaces. The difference in the apparent adsorption Gibbs energy derived from the adsorption isotherm of Py on cs- and smooth gold substrates was accounted for by a correction factor (<i>f</i>) that depends on the roughness (R) of the substrate according to <i>f</i>∝R⁻ⁿ, as expected from Monte Carlo simulation of the model. This agreement indicates that the substrate geometry plays a key role in the interpretation of adsorption isotherms.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas