Coprocessing of the petroleum vacuum residue (XVR) with polystyrene, polypropylene, and Bakelite has been undertaken in a batch reactor under isothermal conditions at atmospheric pressure. The liquids obtained by coprocessing have been characterized by Fourier transform infrared spectroscopy, H-1 nuclear magnetic resonance ( NMR), C-13 NMR, gel permeation chromatography (GPC), inductively coupled argon plasma, and gas chromatography analyses. The main aim of the characterization of the liquid products was to find out the molecular weight distributions as well as the determination of average structural parameters. The GPC analysis showed that the liquids derived from XVR are quite complex, containing a complex range of products. The liquid products obtained from coprocessing showed that there is an interaction of reacting species when they are cracked together. It is also interesting that the liquid products obtained from coprocessing with plastics contained less than 1 ppm of Ni and V. The detailed results obtained are reported.