The effect of structure and composition of calcium phosphate (CaP) nanoparticles namely hydroxyapatite (HA), calcium deficient hydroxyapatite (CDHA) with Ca/P ratio ranging from 1.33 to 1.61 and tricalcium phosphate (β-TCP), on the efficiency of nanoparticles as an ideal drug carrier have been investigated. Ibuprofen, an anti-inflammatory drug was chosen for this study. The CaP nanoparticles were prepared by microwave accelerated wet chemical synthesis method and were characterized by X-ray powder diffraction, infrared spectroscopy, and electron microscopic techniques. The loading and release profiles of ibuprofen from the nanocarriers was studied using UV-Vis spectroscopy. Maximum loading of the drug was observed in β-TCP (75%) followed by CDHA of Ca/P ratio 1.5. Both samples have same Ca/P ratio but have different crystal structure. Low amount of drug loading was observed in HA and other CDHAs which have Ca/P ratio different from 1.5. Although, all the samples exhibits sustained release of ibuprofen for about 7 days, the maximum release was also shown by β-TCP (26%). Among HA and CDHAs, the amount of ibuprofen release increases with increasing Ca/P ratio. The loading and release profile of ibuprofen drug seems to be strongly related to the Ca/P ratio and structure of CaP nanocarriers. © (2013) Trans Tech Publications, Switzerland.