A method is presented for the determination of the internal structure of core-shall latex particles from fluorescence nonradiative energy transfer between a donor and an acceptor chemically bonded to the polymer chains which are supposed to form the core (donor) and the shell (acceptor) of the particles. The method is based on the assumption that these two types of polymer chains are radially distributed inside the particles. The distributions of the polymer labeled with the donor and with the acceptor are directly obtained from the analysis of the fluorescence decay curve of the donor, using a least-squares method coupled with a regularization condition, given the so-called regularization technique of inversion. In the inversion method there is no model and no analytical expression used to describe the concentration profiles of the polymers. We show how this method was tested with known polymer concentration profiles, from which fluorescence decay curves were first constructed and then analyzed. The original polymer distributions were accurately recovered. We show also, with real examples, how this method can give useful information on the internal structure of core-shell particles after their synthesis performed under various conditions, and after annealing of the particles.