The growth of CdS films is studied in a continuous, once-through flow setup. Within a narrow pH range, close to the pH value where spontaneous bulk precipitation occurs, thin coherent layers develop, which are well attached to the steel substrate. initial deposition rate data combined with CdS sol characterization, using light absorbance measurements and scanning electron microscopy, suggest that the prevailing mechanism is crystallization right on the tubular surface. More specifically, the influence of velocity on initial deposition rate as well as the level of estimated activation energy for wall crystallization points to a mass-transfer-controlled process. By studying the morphology of deposits as a function of solution properties (pH, concentration, temperature), flow velocity, and time, conditions are identified for creating (or avoiding the formation of) coherent CdS layers.