Adsorption of associating particles interacting via the Lennard-Jones potential in slit-like pores is studied using the density functional theory. A model of association with one site per particle is considered. Capillary phase diagrams for three values of the association energy are evaluated. We show that the association shifts the entire diagram toward higher temperatures. The critical average densities of the confined fluid, however, are almost independent of the association energy. Our results also demonstrate that the association significantly influences the layering transitions. Copyright 1999 Academic Press.