Alternative sources of the raw material wood, such as wood from short rotation coppice (SRC) and low-value beech wood, were investigated in terms of their suitability for use in the production of wood-plastic composites (WPC). The influence of these wood sources on water absorption, the mechanical properties and the internal structure of the composites was evaluated. The composites based on wood from SRC and on beech wood exhibited a decreased equilibrium moisture content (EMC) and a reduced speed of water absorption in comparison to composites based on wood from Norway spruce. X-ray microtomography revealed a strong alignment of wood particles near the surface regions, as well as dispersion and encapsulation of particles by polypropylene. The investigation of composite performances revealed that the material properties of the WPC derived from these new wood resources were similar and in some cases even superior to those produced with preferred wood sources such as Norway spruce.