Silica-, alumina- and titania-supported Co catalysts with different metal loadings were tested for selective citral hydrogenation in liquid phase. Temperature programmed desorption of hydrogen (H-2-TPD) indicated that the catalysts with the highest unsaturated alcohols selectivities present particular H-Co species. Electron diffraction and XRD measurements revealed that these species would be linked to the presence of Co-0 hexagonal phase. According to the results obtained by TEM and cyclohexane dehydrogenation, these two properties would be present on large Co particles. (C) 2007 Elsevier B.V. All rights reserved.