The present invention relates to a biocompatible injectable filler composition comprising calcium phosphate particles having a porosity of about 10% to about 90%, a BET surface area of about 1 m2/g to about 100 m2/g, and a mean particle size of about 1 micron to about 30 microns, a thermoreversible hydrophilic gelling agent, a carrier comprising water and an optional persistence enhancer and/or volumizing agent, and methods of its use to restore tissue volume and/or to smooth out tissue defects as in soft tissue or deep tissue augmentation.