Herein provided are variable density fluid compositions and methods for using such compositions in a subterranean formation. One exemplary embodiment of the variable density fluid compositions of the present invention comprises a variable density fluid comprising: a base fluid; and a portion of elastic particles, the elastic particles having an isothermal compressibility factor in the range of from about 1.5×10−3 (1/psi) to about 1.5×10−9 (1/psi). Also provided are cement compositions comprising elastic particles, processes for preparing such cement compositions, and methods of cementing in subterranean formations using such cement compositions. One or more elastic particles are mixed with the cement before pumping the cement into a well bore. The elastic particles are preferably composed of an elastomeric material such as a copolymer of methylmethacrylate and acrylonitrile; a terpolymer of methylmethacrylate, acrylonitrile, and dichloroethane; a styrene-divinylbenzene copolymer; and polystyrene.