Short rotation forestry (SRF) is a promising feedstock for production of biofuels via the thermochemical route. Five poplar biomasses (SRF of different clones and ages, and debarked wood) were ground and separated into three particle size fractions: <0.2 mm; 0.2-0.4 mm; >0.4 mm. The characterization of these samples was performed to evaluate the quality and homogeneity of SRF feedstocks. Some major properties related to thermochemical processes were measured: chemical composition, organic and inorganic elemental compositions. The heterogeneity in SRF feedstock properties, resulting from high bark content, appeared to be transferred to particle size fractions. The results obtained highlighted that fine particles below 0.2 mm had very specific properties, close to those of bark. The removal of this fraction would result in a more homogeneous feedstock, avoiding the issue caused by segregation risk for process stability. Such removal of small particles would also modify the biomass properties by reducing bark amount, improving the suitability of SRF feedstock for thermochemical conversion. (C) 2013 Elsevier Ltd. All rights reserved.