This study was designed to examine the effect of operating conditions on essential oil composition and antioxidant activity of coriander cakes. Twenty-nine components were determined in essential oils, which were mostly alcohol monoterpenes. The highest essential oil yields (0.11%) were obtained by the nozzle diameter of 5 mm. The main components of cake essential oil linalool, gamma-terpinene, geranyl acetate, linalyl acetate and camphor showed significant variations with different nozzle diameter. The total phenol contents and condensed flavonoid contents varied between different nozzle diameters; the highest values obtained of small diameters (5 and 6 mm). Significant differences were also found in total tannin contents among different nozzle diameters. The total phenol contents decreased significantly (p < 0.05) when increased the nozzle diameter to 9 mm and reached 9.11 mg GAE/g. The screening of antioxidant activity of the different coriander cakes using the di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium radical (DPPH) assay showed an appreciable reduction of the stable radical DPPH, although small nozzle diameter was the most efficient method with an IC50 reached of 55 mu g/ml as compared with bigger diameter (IC50 = 88 mu g/ml). All the extracts had lower beta-carotene bleaching activity than that of synthetic antioxidant BHA and BHT. Coriander cake extracts presented a very low reducing power ability (EC50 approximate to 700 mu g/ml) compared to ascorbic acid (EC50= 40 mu g/ml).