Two milling modes (shearing and impact) were applied to investigate the hydrogen storage properties of boron. It was found that the shearing mode leads to 2.05 wt% hydrogen trapped in boron, while impact mode to 2.93 wt%. Differential scanning calorimetry (DSC) was used to study thermally induced transformations in freshly milled and aged samples. The DSC traces obtained from freshly milled samples through the shearing and impact modes are dissimilar and are also very different from those obtained from the aged samples. The origins of these differences are discussed in relation to the milling mode applied.