CdS:Li nanoparticles were grown by the thermolysis method using a surfactant to control the nanoparticles growth and the passivity of the dangling bonds. The effect of the Li incorporation on the optical and structural properties of the CdS nanoparticles was studied by means of the optical transmission, photoluminescence, X-ray diffraction and HR-SEM&TEM techniques. The optical energy band gap lies in the interval from 2.7 to 3.6 eV. The photoluminescence spectra present a band with peak at 465 nm, which is indicative of the quantum confinement. The energy peak position (465 nm) is blue-shifted respect to the bulk material (512 nm). Then, one can infer that the energy band gap and the peak intensity vary according to the nominal lithium concentration in the growth solution. An average crystallite size of about 5 nm was estimated by the Brus equation and the Debye-Scherrer formula, and confirm by HR-SEM&TEM measurements.