The growth of Scenedesmus obliquus in photobioreactors was both experimentally investigated and numerically simulated by solving a population balance equation (PBE), accounting for cell growth and division. The PBE is solved using the Finite size domain Complete set of trial functions Method Of Moments (FCMOM) and a wide range of operative conditions, namely both a batch and a continuous reactor under different light intensities, were considered in the experiments and in the numerical simulations. A thorough validation of the mathematical model was performed by comparing the experimental temporal profiles and steady-state values of the cell density, wet weight, cell average mass, and mass distributions of the microalgal culture with the corresponding simulation results. The parameters of the distribution of division mass were identified to fit the experimental data; specifically, from the continuous reactor data, the dependence of the mean division mass from the cell average mass was obtained. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 2702-2710, 2015