The agriculture residues and energy crops have significant energy potential, which is not enough used so far. The agriculture production in Poland, and other countries of EU, gives a huge amount and variety of agriculture wastes. Whereas, energy crops characterise large annual growth at low-quality soil and high energy yields per unit of area. For this study three different agriculture biomass and two energy crops were selected. The samples were characterized in terms of their proximate and ultimate analysis. The main aim of this paper was to investigate the influence of biomass particle size distribution on the combustion and pyrolysis processes using thermogravimetric analysis (up to 600 degrees C at 5, 10 and 20 K/min or 50 K/min heating rate). Two fractions of biomass samples were investigated, smaller (S) size of major fraction smaller than 0.09mm and sample of particle size smaller than 0.425mm named larger (L). The gaseous products generated during pyrolysis process were analysed with GC/MS. Additionally, the kinetics analysis of studied processes was performed. Finally, it was found the particle size influences on the TG/DSC results and consequently significantly on the activation energy of combustion and slightly on pyrolysis of studied biomass samples.