Supercritical carbon dioxide extraction of sesquiterpenes from valerian root was investigated. Extractions from cultivar Arterner zuctung and two wild grown valerian subspecies were performed. The influence of extraction conditions on extraction yield and chemical composition of obtained extracts was investigated at temperatures from 40 degrees C to 50 degrees C and pressures from 10 MPa to 20 MPa. Chemical composition of obtained extracts was analyzed by GC/FID and GC/MS methods. The influence of particle size on extraction process was investigated at 40 degrees C and 10 MPa. The major constituents of supercritical extracts were valerianol, valerenal, bornyl acetate and kessanyl acetate. Optimal extraction conditions for the cyclopentanoid sesquiterepenes isolation, referred to the content of cyclopentanoid sesquiterpenes in extract, were found to be 50 degrees C and 15 MPa. Extract obtained from the cultivar was characterized by the higher content of cyclopentanoid sesquiterpenes, as well as valerenal comparing to extracts from wild grown species. At 40 degrees C and 20 MPa 19.6% of cyclopentanoid sequiterpenes isolated with methanol can be extracted. At 40 degrees C and 10 MPa, 17.4% of cyclopentanoid sequiterpenes isolated with methanol can be extracted. However, the extract obtained with methanol was characterized by the high content (42.51 %) of unwanted isovaleric as well as by the lower content of cyclopentanoid sequiterpenes than the extracts obtained with supercritical carbon dioxide. The process of supercritical extraction was influenced by particle size. In order to simulate the process, mathematical model on the secretory structure scale was derived. Results of the model showed good agreement with the experimental data. (C) 2007 Elsevier B.V. All rights reserved.