The ultrasonic attenuation in solutions of poly(vinyl chloride), poly(vinyl acetate) and different vinyl chloride/vinyl acetate copolymers dissolved in cyclohexanone was investigated. The results indicate that the relaxation spectra can be resolved by curves with two relaxation times. These processes can be explained by the presence of conformational changes of different degree of cooperativity. Comparison of the thermodynamic parameters with conformational energy calculations supports the assumption that the elementary process is a localized single‐bond process. The ultrasonic spectra of the homopolymers solutions are compared with those for statistical and graft copolymers.