In the paper, the study on co-decomposition of polyolefins and thermally unstable methyl alcohol is presented. The process temperature was maintained above 400 degrees C. The pressure at the end of process, depending on the feed composition, was 3-25 MPa. In the first variant, the raw material was polyolefin product, in the form of solidifying liquid, previously partially decomposed. Basing on the satisfactory results regarding the methanol influence on the quality of obtained liquid fractions, extended technological concepts were proposed, in which also solid waste polyolefins can be used without the phase of previous thermocatalytic decomposition. Dissolution of raw polymer is facilitated by paraffin oil addition. The only disadvantage is a large fraction of sulphur, purposely introduced in case of methods that use technological oil. In the last case, waste polyolefins were used, but without oil type additions. Although the efficiency of the liquid product is not as high as in oil technologies, the fractions with satisfactory results are obtained. The results show decomposition of polymer bonds with a simultaneous hydroconversion of unsaturated structures. (C) 2010 Elsevier B.V. All rights reserved.