Hydroxymethylation of furfuryl alcohol with aqueous formaldehyde, yielding selectively 2,5-bis(hydroxymethyl)furan, has been carried out at 338 K in the presence of a highly dealuminated H-form mordenite. Kinetic analysis of the experimental results allows to propose an original kinetic law involving two types of catalytic sites. According to furfuryl alcohol concentration, there is competition, or not, upon these two types of sites.