In order to evaluate how the characteristics of starting HA powders affect their dispersion ability, several tests were made, including particle size distribution, particle morphology (SEM) and rheological measurements of the suspensions. To enable the preparation of concentrated suspensions as high as possible, the influence of deagglomeration procedure on rheological behaviour of hydroxyapatite aqueous suspensions was evaluated. The results revealed significant differences in the dispersing ability of the powders and on the maximum achievable solids loading. In fact, the maximum solids volume fraction that was possible to incorporate in the initial suspension of HA(R) was only 35-vol.%, while with the HAS it has been possible to start from 45-vol.% suspensions. Ball milling revealed to be more efficient than planetary milling in the preparation of HA(R) suspensions, and enabled to achieve a maximum solids volume fraction of 45-vol.% at the end of long milling period, which included successive incremental additions of powder. The powder HAS exhibited a much better dispersing ability, enabling the preparation of 60-vol.% solids only after two hours of planetary milling.