The present work has evaluated the variation of cationic demand in function of refining degree for two unbleached cellulosic pulps: a eucalyptus pulp proceeding from a kraft process and an olive wood pulp proceeding from an organosolv process. In the organosolv process, a mixture of ethanolamine, sodium hydroxide and water has been used. For each kind of pulp, fines percentage, weighted medium length of fines, specific surface, carboxyl group's content, water retention value and cationic demand in function of refining degree have been obtained. Cationic demand has been evaluated by means of colloidal titration. Results obtained suggest the use of olive wood organosolv pulp for industrial purposes need to be enhanced. To achieve the same refining degree than eucalyptus pulp, a lot of refining time was needed. It has been observed also that in eucalyptus pulp, polymer fixation by ionic exchange is higher than adsorption. On the other hand in olive pulp, adsorption of cationic polymers prevailed over electrostatic interactions. The great content of fines in olive pulp and its higher values of carboxyl group's density could explain this behaviour. (c) 2006 Elsevier Ltd. All rights reserved.