Primary pyrolysis and secondary reactions of Japanese cedar (Cryptomeria japonica, a softwood) and Japanese beech (Fagus crenata, a hardwood) wood lignins were studied with open-top and closed-ampoule reactors in N2 at 400-600°C. Milled wood lignins (MWL) isolated from these wood samples were used along with several model aromatic compounds (guaiacol and syringol and their pyrolysis intermediates). Although the low molecular weight products from beech MWL included more syringyl-type of aromatic rings in primary pyrolysis, in the secondary reaction step, the yields of syringyl-characteristic products were quite lower than those of guaiacyl-characteristic products. Contrary to this, the beech MWL and syringol produced more coke. These results suggest that the syringyl-characteristic products are converted preferentially into coke, instead of other low MW products. The molecular mechanisms of these tar conversions are also discussed with the model compound data. Additional OCH3 group in syringyl-unit enhances the coke formation through double opportunity of the OCH3 rearrangement pathway, which includes o-quinonemethide as a key intermediate step for coke formation. © Springer 2011.