The growth mechanism of the ZnS and CdS semiconductor photonic dots grown by metalorganic molecular-beam epitaxy (MOMBE) was studied. In the initial growth process, the delay time of growth initiation was present for small-area ZnS selective growth. The lateral growth during the selective epitaxy was not linear to the growth time, which was explained by considering the diffusion of the Zn and Cd precursors on the {0 3 4} side facets to the (0 0 1) top plane during the growth. The calculation of this model was in good agreement with the experimental results. The apex of the grown structures was studied, and the apex of CdS was sharper than those of ZnS and Zn0.9Cd0.1S. This shows that it is possible to position the CdS layer which has a narrow bandgap only on the apex of the Zn(Cd)S photonic dot as a light-emitting layer.