The nature of the initial interaction between calcium phosphate (CaP) thin films and osteoblasts can be mediated by the outermost surface properties of that material. As such, the phase, crystallinity, stoichiometry, composition and morphology of the CaP surfaces are seen as key parameters that must be accurately controlled in order to influence their potential biofunctionality with respect to osteoblasts. Hydroxyapatite [HA – Ca₁₀(PO₄)₆(OH)₂] has been extensively studied due to the structural and chemical similarities demonstrated with the main inorganic constituent of bone tissue and teeth. However, it is well documented that biological hydroxyapatite, which forms the mineral phases of calcified tissues, differ from pure and synthetically produced HA. Biological apatite is comprised of a mixture of calcium phosphate phases and trace elements, e.g., strontium, zinc, magnesium and silicon. As such, when designing CaP biomaterials for clinical use (both bulk materials and coatings) one proposed route would be to introduce multiple ionic substitutions into HA in order to mimic the complex chemistry of human bone and thereby improve the biological performance of such materials, both in vitro and in vivo. This presentation will explore a novel approach to depositing substituted and co-substituted CaP systems onto a range of different substrates types, namely metal and polymers. In particular, this presentation will examine how the surface properties of bioinert polymers, such as Poly(etheretherketone) (PEEK) accurately controlled in order to provide an enhanced in vitro performance. The presentation will also look at how resorbable magnesium implants can also be manipulated to provide both enhanced bioactivity and to provide a route to control how they resorb in a physiological environment.