This paper analyzes the role performed by rubber from tire in coal-tire coprocessing when tire is added to coal hydrogenation. A low-rank coal (SAMCA, Spain) and discarded scrap tires (steel thread and the textile netting were previously removed) were batch processed in tube reactors at various hydrogenating atmospheres (10, 7.5, 5, and 1 MPa of hydrogen) and in inert atmosphere (1 MPa of nitrogen) for 30 min at 400 degrees C. Two feed mixtures, 80% coal/20% rubber (4/1 ratio), and 20% coal/80% rubber (1/4 ratio), and both raw materials were processed separately. While rubber does not show variations with the process atmosphere, coal significantly varies with the pressure and the hydrogenating inert atmosphere. The selected process conditions were critical in order to elucidate the role performed by rubber from tire in coal hydrocoprocessing. The percentages and characteristics of the conversion products help to clarify the performance of rubber as a hydrogen donor, as a hydrogen transport and as a solvent. It is concluded that the improvement in quantity and quality of conversion products caused by tire addition to coal hydroconversion does not seem to be due either to the as solvent role or to the hydrogen transport role of rubber. The results obtained point out that rubber behaves as a hydrogen donor. In addition, the synergism observed in coal-rubber hydrocoprocessing and the less aromatic nature of the radicals from tire pyrolysis involved in the process are very helpful in improving the nature of the obtained oils.