Flocculation of precipitated calcium carbonate induced by polyelectrolytes was monitored using light diffraction scattering (LDS), which can supply the complete kinetic curve for the flocculation process. Cationic polyacrylamides of very high molecular weight with different charge densities and degrees of branching were tested. The effects of the charge density, degree of branching, and concentration of the flocculant on the flocculation process, as well as on floc resistance and reflocculation capacity, were investigated. Moreover, floc structure was evaluated through the calculation of the fractal dimension using the scattering matrix. The study demonstrates the benefit of using LDS for the evaluation, in a single test, of flocculant performance in the different stages of flocculation: aggregation, stabilization, deflocculation, and reflocculation.