We have investigated unlignified tension wood and normally lignified wood celluloses in Populus maximowiczii with particular reference to the composition of two crystalline phases I-alpha/I-beta (triclinic/monoclinic). Four independent techniques, which enable us to detect the two phases, CP/MAS C-13 NMR, Fourier transform infrared microscopy, selected-area electron diffraction, and X-ray diffraction were applied. Because of the low crystallinity of wood celluloses, particularly in the case of celluloses in the lignified cell wall, no single method was decisive enough to be able to determine the composition of the two phases as one can with highly crystalline materials. The Ig dominant structure (monoclinic crystal type) was, however, preferred for both tension and normal wood celluloses.