Activated carbons from coals and agricultural by-products have been prepared following different experimental procedures. The surface area, pore texture and ζ-potential of the activated carbons have been studied. These characteristics depended on: raw material used, activation process and pretreatments to steam or carbon dioxide activation. Adsorption at 298 K of phenolic compounds such as: phenol, p-cresol, m-aminophenol, p-nitrophenol, m-chlorophenol and o-chlorophenol from aqueous solutions on the activated carbons under static and dynamic conditions has been studied. The adsorption capacity of the activated carbons depended on the surface area and porosity of the carbon, the solubility of the phenolic compounds, the hydrophobicity of the substituent and the solution pH. The relative affinity of the phenolic compound toward the surface of the carbon was related to the electron donor-acceptor complexes formed between the basic sites on the surface of the carbon and the aromatic ring of the phenol. The yield of the adsorption process under static conditions was higher than under dynamic conditions because the diffusion problems in the latter case are greater. The characteristics of the carbon beds have been related with the textural characteristics and the chemical nature of the activated carbons.