A modified chemical vapor transport system is developed to grow ZnSe single crystals from zinc-selenium source materials, where iodine serves as the chemical transport agent to avoid the kinetics limitations of the congruent sublimation conditions. ZnSe crystals with different crystalline quality are obtained under various growth conditions. The thermodynamic properties of Zn-Se-I-2 system are studied by combining the mass conservation with the vapor-solid reactions related to crystal growth. The mass transport is analyzed by using the diffusion-convection mathematical model. Depending on initial iodine concentration and the designed temperature difference between source zone and growth zone, the optimum growth conditions can be predicted based on the calculated maximum growth rate. Comparing growth results with theoretical analysis indicates that Zn-Se-I-2 system affords a feasible route to grow ZnSe crystals. High quality ZnSe crystal can be achieved under the theoretically optimized growth conditions. (C) 2014 Elsevier B.V. All rights reserved