The relaxation behavior of a series of ether-ketone oligomers, considered as model compounds of poly(ether-ketone-ketone), was studied by means of dielectric spectroscopy. The dynamics of the a relaxation of ether-ketone model compounds as compared with that of poly(aryl-ether-ketone-ketone) (PEKK) (50/50), shows up differences which can be attributed to the variation of inter- and intramolecular correlations with the chain length. Model compounds exhibit a nearly similar degree of cooperativity regardless the differences in T-g values. The PEKK (50/50) polymer exhibits stronger cooperativity than the oligomers suggesting that in poly(ether-ketone-ketone)s molecular motions above T-g extend to more than one monomeric unit.