Electrosynthesis appears as one of the best methods to prepare advanced materials under the form of coatings or thin layers. The advantages of such a process are economic (low investment for an easy composition control and large area deposition) and ecologic (no product loss). Yet, aqueous electrolysis exhibits two serious drawbacks: the low crystallinity of the electrodeposited material (due to the low working temperature) and the hydrogen discharge (preventing electrodeposition of very electronegative elements as Ga). In this context, using high-temperature molten salts as electrolytes is a promising way to elaborate materials with tailored structures and properties. This method was successfully applied to the electrodeposition of the semiconductor ZnSe which is a good candidate for window layers in thin film solar cells. Electrochemical investigations performed in molten CaCl2-NaCl mixture at 550 degrees C are reported. ZnSe was electrodeposited on glass sheets covered with SnO2. Optimized melt composition and potential led to yellow, transparent and adherent thin films containing up to 90% well crystallized ZnSe with a ratio Zn/Se close to 1 and a 1-mm grain size. The energy band gap measured is 2.5 eV.