In this study, we present comprehensive experimen-tal results related to the conversion from the normal ferroelectric P(VDF-TrFE) copolymer to a relaxor ferroelectric P(VDF-TrFE-CFE) terpolymer due to the in-troduction of bulky CFE termonomers into the crystalline phase. Compared with the copolymer, the relaxor terpoly-mer exhibits high electrostrictive response and high room temperature dielectric constant. The experimental data from XRD, FTIR, DSC, and dielectric studies indicate that the macro-polar crystallites in the normal ferroelec-tric copolymer are transformed into a non-polar phase with local nano-clusters. There is no indication of an F-P transition in the terpolymer investigated.