The growth of cubic CdSe and CdxZn1-xSe on (100) GaAs by MOVPE using dimethylcadmium, dimethylzinc and dimethylselenide is reported. It is shown that CdSe growth can be achieved at much lower temperatures than for ZnSe when (CH3)2Se is used as the group VI source. Single crystal alloy layers can be grown across the entire composition range from ZnSe to CdSe. However layers are zinc rich compared to the gas phase Cd:Zn ratio. The layer quality - as determined by microscopy, X-ray diffraction and photoluminescence - is good for low values of x, but deteriorates with increasing Cd composition.