For many years, fossil fuels have played a main role in providing energy in various sectors, including traortation. Today, negative impacts of crude oil-based fuels necessitate finding alternatives. Lignocellulosic biomass is a good candidate to produce biofuels, such as bioethanol and biogas. In this research, the effect of extractives on the bioethanol and biogas production has been examined to improve the production yield. For this purpose, two types of lignocellulosic material, pinewood and rice straw, were selected for. At first, extractives of these two substrates were extracted using soxhlet, then anaerobic digestion process, enzymatic hydrolysis and simultaneous enzymatic hydrolysis and fermentation of pinewood and rice straw were performed in the presence of different concentrations of extractives. The amount of methane produced from pinewood extracted with water was about 87 ml/g.VS, which in the presence of 80 g/l of extractives from pinewood with water decreased to less than 1 ml/g.VS. The amount of biogas produced from rice straw extracted with water was 244 ml/g.VS, which reduced to 55 ml/g.VS with the addition of 80 g/l of rice straw extractives extracted by water. Adding extractives from pinewood extracted by ethanol to biogas production process from pinewood reduced the quality of produced biogas. The production of biogas from rice straw in the presence of rice straw extractives extracted by ethanol, increased biogas production from 169 ml/g.VS to 528 ml/g.VS, resulting 212% increase in biogas production. Then, the enzymatic hydrolysis of pinewood in the presence of its extractives, extracted by water and ethanol, and enzymatic hydrolysis of rice straw in the presence of its extractives extracted by water and ethanol, were performed. In all four hydrolysis processes, the presence of extractives did not have much effect on the hydrolysis efficiency. Subsequently, simultaneous enzymatic hydrolysis and fermentation of pinewood and its extractives extracted by water and ethanol, and simultaneous enzymatic hydrolysis and fermentation of rice straw and its extractives extracted from water and ethanol, have been performed. Results showed that the extracted materials from pine wood with water have inhibitory effect on this process and the yield of produced ethanol decreased (from 18.5% to 5%). The results of simultaneous enzymatic hydrolysis and fermentation of rice straw and its extractives extracted by water, also indicate the inhibitory effect of these materials on fermentation. The process of simultaneous enzymatic hydrolysis and fermentation of pinewood, and its extractive materials extracted by ethanol had a different result. The presence of extracted materials not only had no inhibitory effect, but also improved ethanol production efficiency (from 18.5% to 28%). Simultaneous enzymatic hydrolysis and fermentation of rice straw and its extractives extracted by ethanol also showed an inhibitory effect of extractive materials and reduced the yield of ethanol from 49% to 32%. The phenol and tannin compounds in the substrate and extractives were also measured by phenol and tannin tests. In this test, it was found that the amount of phenol in rice straw is higher than pinewood. The gas chromatography-mass spectrometry was also used to identify the compounds in these extractives. The results of this analysis indicated that 4-benzyloxy-4-[2,2-dimethyl-4-dioxolanyl] Butyraldehyde and abietic acid are the main components of pinewood extractives extracted by water and ethanol, respectively. Main components of the extractives from rice straw extracted by water and ethanol, are 3-hydroxy-spirost-8-n-11-n and Guaiazulene, respectively. Key words : lignocellulosic biomass, extractives, biogas, bioethanol, enzymatic hydrolysis, simultaneous hydrolysis and fermentation (SSF)