To understand better the effect of La2O3 as primer for the preparation of honeycomb supported La0.9Ce0.1CoO3 +/- delta catalyst, some samples were prepared starting from different La-precursors. Physical and morphological properties of both the primer-coated honeycomb and its precursors (as-prepared and after thermal treatment at different temperature) have been investigated by TGA, TPD-MS. XRD and SEM. Calcination at high temperature brought about a rearrangement of both primer and active phase morphology. When La acetate was used as precursor, such a transformation seemed not to alter substantially the morphology of the primer layer, leading to a poorer anchoring to the support, with deep cracking and exfoliation of the La oxide platelets so formed. By contrast, when the primer precursor was La nitrate, the higher reactivity of the hydroxynitrates, forming during calcination, with respect to both the active phase and the honeycomb, led to a more uniform and compact La2O3 layer, anchoring much better the perovskite to the monolith support. (C) 2004 Elsevier B.V. All rights reserved.