Abstract : The richness of the apatite structure is an extraordinary ability to accept substitutions and vacancies and this property is intimately related to its adaptability to the biological functions of different tissues. The apatite structure can incorporate a wide variety of ions, of the same or of different charge, which affect both its cationic and anionic sub-lattices. If necessary, charge compensation can be achieved through the combination of ions of different charges and/or through the creation of vacancies, leading to apatites with complex formulae. This presentation will illustrate how multinuclear solid state NMR methods can be efficiently used to describe the local environment of carbonates and silicates in substituted hydroxyapatites, HAp. Two examples will be presented : silicon- substituted biphasic calcium phosphate bioceramics and carbonated hydroxyapatite layer grown on sol-gel glass soaked in SBF.