The cyclo-tetraphosphates of the type Cd2-xZnxP4O12 have been synthesized. The synthesis is based on a thermal procedure making use of the reversible transformation of cyclo-tetraphosphates to higher linear phosphates. This is the method used in our laboratory for synthesis of special pigments of binary cyclo-tetraphosphates, especially of some bivalent metals combined with zinc. The compounds prepared have been evaluated from the standpoint of their structure, colour hue, density and thermal stability.