Fennel (Foeniculum vulgare Mill.) is an important aromatic plant mainly used in beverages in Greece, in pharmaceutical and cosmetic products, and in confectionaries. There is a need to know which cultivar and N-fertility rate are the most appropriate for a high essential oil content of good quality. Three cultivars, two of sweet fennel from Greece and Turkey, and one bitter fennel from Bulgaria, were evaluated for their essential oil yield and quality under three levels of nitrogen (60, 80 and 100 kgиha -1 ). Essential oils yield ranged from 2.35 to 9.58%, and percentages of the main constituents: anethole (64.30-82.30%), L-fenchone (0.90-20.60%), methyl chavicol (2.60-4.00%) and limonene (3.30-7.20%) varied significantly among the cultivars. Essential oil yield and composition were affected by cultivar, but not by nitrogen rate. The sweet cultivar from Greece yielded higher amounts of essential oil; the cultivar from Turkey had higher amounts of anethole than did the bitter cultivar from Bulgaria, though L-fenchone was higher Paschalina S. Chatzopoulou