In this study, the compounds in the liquid phases produced from the liquefaction of the lignocellulosic material have been investigated. For this purpose, liquid phases obtained from liquefaction of cotton stalk and cellulose and paper plant solid waste treated with aqueous acetic acid (HAc) or sodium hydroxide (NaOH) (15% by mass) at high initial inert gas pressure and high temperature were selected for the analyses. Phenolic compounds, cyclic compounds, unsaturated aliphatic hydrocarbons and other compounds (benzoquinone, aliphatic alcohols) and furans were identified by TLC, GC and GC/MS equipped with capillary column. It was concluded that lignocellulosic substances were converted into various water-soluble compounds in the liquefaction processes. Furans and cyclic ketones may be cyclization products of dicarbonyl intermediates formed by aldol condensation reaction of low-molecular mass compounds formed from degradation products of the initial stages of liquefaction. (C) 2004 Elsevier B.V. All rights reserved.