The results of a systematic study of spiro-cyclotri/tetraphosphazenes with ferrocenyl pendant arm on the basis of correlation between structural parameters were presented. The main parameters were obtained from Xray crystallography and (31) P NMR results in order to investigate the relationship between the d P spiro shift values and endocyclic and exocyclic NPN bond angles, and electron density transfer parameters. Structural parameters derived from 11 types of the ferrocenyl cyclophosphazene derivatives with 5- to 7-membered spiro-rings introduced to the literature from our research group were studied and compared with each other.