Five different biomass samples were selected for this study, including miscanthus, distillers dried grain (DDG), wheat shorts, wheat straw and UK wood. These samples were thermochemically treated to alter the lignin, cellulose and hemicellulose composition. Thermogravimetric tests were carried out on these samples to determine thermal behaviours of biomass and its individual lignocellulosic components. The relationship between thermal behaviour of biomass and its corresponding lignocellulosic composition was revealed. The reliability of this relationship was proved by thermogravimetric analysis of samples of artificial biomass prepared by mixing commercially obtained lignin, cellulose and hemicellulose at various blending ratios. It is shown that actual biomass profiles can be predicted with some degree of accuracy based on the lignocellulosic composition.