The phosphoric acid group was introduced into the poly(vinyl alcohol) (PVA) and ethylene/vinyl alcohol copolymers (EVA) structures via H3PO4/urea and POCl3/pyridine systems. The structure of phosphorylated polymers was characterized by H-1 and P-31 {H-1} NMR and pH titration analyses. It was found that H3PO4/urea system leads to formation of soluble phosphorylated polymers with a low degree of phosphorylation (DP) or insoluble phosphorylated polymers with a high DP while POCl3/pyridine system results in the crosslinked structure. Then, an efficient and straightforward method for the introduction of pendant diemethyl phosphate groups into EVA via reaction with in situ synthesized dimethyl iodoophosphate was proposed. Resulting polymers were characterized by H-1 and P-31 {H-1} NMR spectroscopies. The phosphorylated polymers with high DP and without any crosslinked structure were achieved. To remove one or both methyl groups, the phosphate groups were subsequently (mono)-dealkylated using NaI and ClSi(Me)(3)/NaI, respectively.