A model to correlate and predict the release behavior of drugs from hydrogel nanoparticles is presented in this paper. The nanoparticle is considered as a combination of a shell of an elastic semipermeable membrane and a core of a fluid phase (After swelling equilibrium). The fluid core consists of network building materials and other components that are able to partition in hydrogel nanoparticle phase and surrounding coexisting liquid phase, and is enveloped by the membrane shell. The excess Gibbs energies of the hydrogel nanoparticle phase and the surrounding coexisting fluid phase are expressed e.g. using UNIQUAC equation with “free-volume” contribution for non-ionic solution and VERS-model for ionic one. The elastic properties of polymer network could be described, for example, by the “phantom network” theory. A model to correlate and predict the release behavior of drugs from hydrogel nanoparticles is presented in this paper. The nanoparticle is considered as a combination of a shell of an elastic semipermeable membrane and a core of a fluid phase (After swelling equilibrium). The fluid core consists of network building materials and other components that are able to partition in hydrogel nanoparticle phase and surrounding coexisting liquid phase, and is enveloped by the membrane shell. The excess Gibbs energies of the hydrogel nanoparticle phase and the surrounding coexisting fluid phase are represented eg using UNIQUAC equation with “free-volume” contribution for non-ionic solution and VERS-model for ionic one. The elastic properties of polymer network could be described, for example, by the “phantom network” theory.