Structural and textural characteristics of hydrodesulfurization catalysts [NiO (COO)-MoO3/gamma-Al2O3] in oxide and sulfide forms were investigated by XRD, DRS, SEM and LTNA methods, after accelerated laboratory aging. The results pointed out to "surface spinel" formation and possibility of their stabilizing effect with respect to the support. Based on experimental DRS data of electronic d-d transitions of Ni(II) and Co(II) promoter ions in the catalysts, the parameter of crystal-field splitting 10D(q) and energies of electronic states of promoter ions in the spinel-like structure were calculated. The most probable scheme of molecular orbital has been proposed.