The stereoregularity of poly (methyl methacrylate) (PMMA) polymerized in Karamatsu (Larix leptolepis GORDON) and Yellow seraya (Shorea faguetiana HEIM), using benzoyl peroxide as an initiator was investigated. The homopolymer and the grafted polymer onto cellulose and lignin were isolated from the wood-plastic combination, and their stereoregularities were quantitatively determined with a 100 MHZ NMR spectrometer. The stereoregularities of the grafted polymer onto cellulose and lignin were different from that of PMMA which was formed in ordinary radical polymerization. The stereoregularities of the grafted polymer onto wood components were numerically almost equal, but that of the grafted polymer onto lignin for Yellow seraya. Based on the experimental results, the effect of wood components on the stereoregularity of the polymer which was formed in wood was discussed.