The objective of this work was to evaluate the relative role of the calcium phosphate surface chemistry and surface topography on human osteoblast behavior. Highly dense phosphate ceramics (single-phase hydroxyapatite HA and beta-tricalcium phosphates TCP) presenting two distinct nano roughnesses were produced. Some samples were gold-sputter coated in order to conveniently mask the surface chemical effects (without modification of the original roughness) and to study the isolated effect of surface topography on cellular behavior. Our results indicated that the nanotopography of the studied ceramics had no effect on the cellular adhesion (cell spreading, focal contacts and stress fibers formation). On the contrary, strong topographical effects were verified on cell proliferation and differentiation. Moreover, the phosphate chemistry was responsible for changes in adhesion, proliferation and cell differentiation. On TCP, it was shown that the main influent parameter was surface chemistry, which negatively affected the initial cell adhesion but positively affected the subsequent stage of proliferation and differentiation. On HA, the main influent parameter was surface topography, which increased cell differentiation but lowered proliferation.