The present invention concerns spheroidal alumina particles characterized by a BET specific surface area in the range 150 to 300 m2/g, a mean particle diameter in the range 1.2 to 3 mm and a particle diameter dispersion, expressed as the standard deviation, not exceeding 0.1, a total pore volume, measured by mercury porosimetry, in the range 0.50 to 0.85 mL/g, a degree of macroporosity within a particle of less than 30%, and in which the dispersion of the diameters of the macropores, expressed as the ratio D90/D50, does not exceed 8.The invention also concerns processes for the preparation of said particles as well as catalysts comprising said particles as a support, and their use in catalytic hydrocarbon treatment processes, in particular in a catalytic reforming process.