Hydrothermal liquefaction, a thermochemical conversion process, is an effective method used for converting biomass into the liquid products. In this study, Datura stramonium L. plant stems have been used as biomass source. The experiments have been carried out using a cylindrical reactor (75 mL) with (cole-manite and borax) and without catalyst at temperatures of 250, 300, 350 and 380 degrees C. At the trials, it has been determined that formation of gas products has been dominant after 300 degrees C temperature and there has been a decrease in the liquid product efficiency after this temperature. The produced liquids at 250, 300, 350 and 380 degrees C in liquefaction were analyzed and characterized by elemental analysis, GC-MS and FT-IR. According to the analysis, highest numbers of different types of compounds were identified as 64 at the trials performed at 300 degrees C by GC MS. Thirty-nine, 54 and 60 different types of compounds were identified respectively at 250,350 and 380 degrees C. (C) 2015 Elsevier B.V. All rights reserved.