During last 20-30 years many researchers have paid attention to studies of exploitation properties of wood polyolefine composites (WPC) [1]. The most useful from the wide selection of polyolefines are high density polyethylene (HDPE) or polypropylene, but as reinforcement of WPC different waste materials comprising lignocellulose fibres often are used. Such materials also are a lot of waste which arises for example in plywood production industry. In this work for reinforcing of HDPE we approbated one of the waste product-plywood sanding dust (PSD), which contain wood fibres fractions with different length (l). The main fraction (68%) are fibres with length l=0.25-0.5 mm. Our previous studies [2] showed that PSD is promising filler for PP reinforcing. Additions of the PSD up to 40 wt.% increases tensile and flexural modulus, but decreases deformation ability of PP matrix, impact strength, water resistance and fluidity of composite melts. Modification of composites with interfacial modifier maleated polypropylene (MAPP up to 5-7 wt.%) considerably improve all the above-mentioned properties. Very popular matrix for preparing WPC also are different types of recycled HDPE [3]. The goal of this study is to determine PSD influence (30, 40, 50, 60 wt.%) on virgin HDPE (type Liten PND 33-300, MFI=15.58g/10min.) containing WPC physical-mechanical and other exploitation properties. As interfacial modifier Licocene PP MA-7452 (1,3,5 wt.%) and polyvinylbutiral (PVB 5,10 wt.%) were used. Composites were prepared by mixing on two rolls mill, then cooled, granulated and pressed in 1 mm thick sheets for microhardness measurements by Vikers M-41. Flexural and impact strength tests were done for standard specimens (EN ISO 178 and ASTM D 256 M respectively), bars produced by injection moulding. Melt fluidity (melt flow index-MFI) was estimated by standard ASTM D 1238. Water resistance measurements were done according to standard ASTM D 570-88.