Pure and lead doped ZnS nanoparticles have been successfully synthesized by chemical precipitation method. Structural analysis using X-ray diffraction confirms the cubic phase of ZnS and formation of an additional cubic phase of lead sulphide in lead doped ZnS nanoparticles. Increase in the band gap of the doped nanoparticles is consistent with the reduction of crystallite size which lies in the quantum confinement regime. A broad green emission was observed in photoluminescence spectra of lead doped ZnS nanoparticles. The green emission arises due to the presence of lead ions at zinc lattice sites in the host lattice of ZnS. Dielectric measurements reveal that dielectric constant is higher for the doped samples indicating that value of the dielectric constant can be tuned by adding suitable amount of the dopant although dielectric losses in these samples are higher and further investigations are required. (C) 2016 Elsevier B.V. All rights reserved.