Introduction - Vetiver root oil is known as one of the finest fixatives used in perfumery. This highly complex oil contains more than 200 components, which are mainly sesquiterpene hydrocarbons and their oxygenated derivatives. Since conventional GC-MS has limitation in terms of separation efficiency, the comprehensive two-dimensional GC-MS (GC x GC-MS) was proposed in this study as an alternative technique for the analysis of vetiver oil constituents. Objective - To evaluate efficiency of the hyphenated GC x GC-MS technique in terms of separation power and sensitivity prior to identification and quantitation of the volatile constituents in a variety of vetiver root oil samples. Methodology - Dried roots of Vetiveria zizonioides were subjected to extraction using various conditions of four different methods; simultaneous steam distillation, supercritical fluid, microwave-assisted, and Soxhlet extraction. Volatile components in all vetiver root oil samples were separated and identified by GC-MS and GC X GC-MS. The relative contents of volatile constituents in each vetiver oil sample were calculated using the peak volume normalization method. Results - Different techniques of extraction had diverse effects on yield, physical and chemical properties of the vetiver root oils obtained. Overall, 64 volatile constituents were identified by GC-MS. Among the 245 well-resolved individual components obtained by GC x GC-MS, the additional identification of 43 more volatiles was achieved. Conclusion - In comparison with GC-MS, GC x GC-MS showed greater ability to differentiate the quality of essential oils obtained from diverse extraction conditions in terms of their volatile compositions and contents. Copyright (C) 2009 John Wiley Sons, Ltd.