Compacted graphite iron exhibits a unique combination of properties between grey cast iron and ductile iron. To obtain vermicular graphite, the modification is conducted by addition of S- and O-affine elements into the melt. In particular, Mg, Ce, La and Y have proven to be suitable modification agents in the foundry practice. Next to the addition of modifying elements, the cooling speed and the inoculation state of the melt are of importance for the production of the desired graphite form. This work compares the effects of the single element modification in different inoculation states as well as in different wall thicknesses. Additionally to the graphite shape the chilling tendency was investigated in the microstructure as well as by hardness testing. The systematic study elucidated a remarkable difference in the modification properties between Mg and the rare earth elements used depending on wall thickness as well as affecting the width of the processing window for compacted graphite. Thermodynamic calculations and scanning electron microscopy-investigations were used to interpret the different mechanisms of the modification agents.