The main goal of scientific researches in the field of bone tissue engineering is to synthetize a material that mimics natural bony tissue, in order to use it as a bone implant. The material has to be chemically and structurally similar to bony tissue, and possess required properties, such as biocompatibility, bioactivity, osteoinductivity, biodegradibility and mechanical support. Hydroxyapatite (HAp) has shown all of the above mentioned properties and is very similar to biological apatite, that is present in natural bony tissue. Therefore, the aim of this research is a structural characterization of synthetized HAp obtained from biogenic source, along with strontium substitution (0, 1, 5 and 10 mol%), that is crucial for bone growth and is used for treating osteoporosis and similar diseases. Result of using biogenic source is multi-substituted nonstochiometric HAp, which is more similar to biological apatite than synthetic HAp. Various trace elements present in HAp obtained from biogenic source are crucial for bone growth. Prepared samples were analysed by X-ray diffraction analysis (XRD), in order to determine their phase composition. Obtained results were additionally processed by Rietveld refinement method using software, DIFFRAC.SUITE TOPAS V.5.0. To determine thermal stability of samples, they were heat-treated at 1200 °C and analysed by X-ray diffraction and using Rietveld refinement method. Prepared calcium phosphates were composed of hydroxyapatite (HAp), octacalcium phosphate pentahydrate (OCP) and amorphous calcium phosphate (ACP), while heat-treated samples were composed of β-tricalcium phosophate (β-TCP) and amorphous calcium phosphate (ACP). Along with increase of Sr-substitution level, lattice parameters of obtained CaPs increased, as a result of larger radius of substitued strontium ion. Strontium ion occupies in hydroxyapatite Ca1 site, in OCP sites Ca3, Ca4, Ca7 and Ca8, while in β-TCP it occupies sites Ca1, Ca2, Ca3 and Ca4.