ZnSe thin films have been prepared by inert gas condensation method at argon gas partial pressure of 2ï´10-1 mbar and room temperature (298 K). The influence of thermal annealing in vacuum, on optical and electrical properties of ZnSe films have been investigated using optical transmission and conductivity measurements. The absorption coefficient (á) and band gap (Eg) are calculated using transmission curves. Optical transmittance measurements indicate the existence of direct allowed optical transition with a corresponding energy gap in the range of 2.80-3.00 eV. The dark conductivity (ï³d) and photoconductivity (ï³ph) measurements, in the temperature range 253-358 K, indicate that the conduction in these materials is through an activated process having two activation energies. ï³d and ï³ph values increase with the increase in the crystallite size on annealing. The values of carrier life time have been calculated and are found to increase with the increase in the crystallite size on annealing. Results show that the above properties change appreciably after the thermal treatment.