The chemical bath deposition of CdSe layers from cadmium acetate + sodium selenosulfite solutions was studied by means of quartz crystal microbalance (QCM) experiments, combined with electron microscopy observations and energy-dispersive X-ray analysis. Nanocrystalline deposits with the cubic blende structure are obtained showing confinement effects. From mass vs. time measurements and modeling of the time derivative, it is established that the nucleation and growth process occurs via two steps : the first corresponds to an instantaneous nucleation of cylindrical nuclei, with two-dimensional growth until complete coverage of the substrate; the second consists of a three-dimensional instantaneous nucleation and growth process occurring on sites randomly distributed on the evolving surface. The addition of silicotungstic acid to the deposition bath is shown to influence the growth kinetics of the CdSe deposit. From analysis of the kinetic data, and from the transmission and scanning electron microscope images, it is suggested that the chemical deposition of CdSe occurs through the aggregation of colloids and not according to an atom-by-atom mechanism.