We report on the growth of ZnxCd1-xSe pseudo-binary alloys on (0 0 1) InP substrate, at temperature of 360 degreesC, by organometallic vapor phase epitaxy. The compositions x in the alloy were estimated from the peak energies in the room temperature cathodoluminescence (CL) spectrum and were confirmed by X-ray diffraction (XRD), We found that the composition in the alloy was difficult to control by adjusting the precursor flow rates and the flow ratios. Moreover, the growth is unstable by phase separation of binary compounds and formation of novel structures with compositions x close to 0, 0.25, 0.5, 0.75 and 1. The formation of these structures is complicated and does not depend on the precursor flow rates and flow ratios during growth. We also found that Se treatment of InP substrate before the growth facilitates the formation of these structures.