The mixed phases obtained by cation or anion cross substitu-tion are of particular interest due to the" tailoring" possibilities in the physical properties [2]. As measured by X-ray diffraction, the lattice constants in the mixed phase ZnCa2 (S, Se1-x) 4 vary with composition x in a nearly linear way between the va-lues of the end members. As already found in pseudobinary mixed compounds [3], the NN distances remain approximately constant with x. The second main task of this EXAFS work was to check if this behaviour is presented also by pseudoternary anion mixed compounds.