The nano dispersions (colloids) of Cadmium Sulfide, Zinc Sulfide and Cadmium Zinc Sulfide were prepared by modified metathesis reaction between CdCl₂, ZnCl₂ and Na₂S. The prepared sulfides were embedded in polystyrene to form nano-composites. The size, morphology and composition of the nanoparticles on the surface of the composites were examined by using UV/VIS Spectroscopy, Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive Spectroscopy (EDS) and Particle Induced X-ray Emission (PIXE). The UV-spectrum shows a shift in the band gap towards high energy while the High Resolution Transmission Electron Microscope (HRTEM) analysis shows well resolved nanoparticles with particle sizes between 2-10 nm. The SEM shows that the nanoparticles are in form of nano clusters. The blue shift of the absorption band makes it possible to evaluate the size of the nanocrystallites, which is in agreement with that obtained from HRTEM. The composition as revealed by the EDS shows that the ratios of Cd:S, Zn:S and Cd:Zn:S are approximately 23:20, 58:42 and 32:35:33, respectively. The PIXE spectra confirmed the presence of expected elements and also reveal the presence of impurities.