Raw material recycling is an important and necessary means of material reutilization of plastics. Processes and plants which are already available should be used. Visbreaking is a relatively inexpensive residue upgrading process. Therefore investigations in coprocessing of thermal pretreated plastics with vacuum residue - the conventional starting material - were performed in a laboratory vis-breaker. The consistency of the mixtures were estimated with instrumental analytical techniques. The mixtures were reacted under mild thermal cracking conditions. Conversion product distribution and product properties were measured. The addition of pre-treated plastics in specific percentages does not lead to any significant changes in the process and product parameters.