Combustion rates and completeness of aerosolized spherical aluminum powders and flakes are compared using constant volume explosion experiments. The comparison of particles and flake sizes was made based on their specific surface areas determined using the Brunauer-Emmett-Teller (BET) method and respective "BET diameters." It is observed that the rates of pressure rise and respective rates of flame propagation were higher for spherical aluminum powders with BET diameters of about 2 to 5 mum compared to aluminum flakes for which the respective BET diameters were under 1 mum. In agreement with the flame propagation rates, the overall completeness of combustion was also higher for spherical powders compared to flakes. It is suggested that aerosolized flakes could be agglomerated in gas flows more than spherical particles causing their inferior combustion performance.