A great wealth of structural information about phosphazenes can be gleaned from the combined spectroscopic and crystallographic data. When data from (31) P NMR spectroscopy and X-ray crystallography are put together like pieces in a puzzle, a number of correlations can be obtained for phosphazene derivatives. A systematic study concerning the correlations among the structural parameters (e.g., (31) P NMR data, endocyclic/exocyclic NPN bond angles and bond lengths) revealed some characteristics of mono- and di-spirocyclophosphazene derivatives bearing 4fluoro/nitrophenylmethyl pendant arm/arms. These correlations include the relationship between the delta P-spiro shifts, the values of electron density transfer parameters Delta(P-N), and the endocyclic and exocyclic NPN bond angles of the cyclophosphazenes. The structural parameters were compared with each other for 19 compounds of 5 different architectural types of cyclophosphazenes with 5- to 7-membered spiro-rings.