This study was carried out to determine the total antioxidant activity of selected green vegetables like kale and spinach. The antioxidant activity was expressed in radical scavenging activity (RSA). The generation of the DPPH· (1,1-diphenyl-2-picrylhydrazyl) free radical forms the basis of one of the spectrophotometric methods that has been applied to the measurement of the total antioxidant activity of extracts and solutions of pure substances. Among examined vegetables, spinach showed the highest total antioxidant activity. RSA values for samples of frozen spinach varied from 16.2% to 42.6%, but RSA for fresh spinach did not exceed 19.8%. Kale extracts were obtained by use of supercritical fluid extraction. The highest antioxidant activity was found for the first fraction of extracts, and it was 14.2% (for fraction obtained at pressure 258 bar and 5% methanol addition). Afterwards, lutein belonging to carotenoid group was determined in plant extracts by means of HPLC–UV-VIS. The concentration values of lutein ranged between 0.43 and 0.88 mg/g for three frozen spinach samples and 0.83 mg/g for fresh spinach. Lutein, has also antioxidant properties; therefore, RSA was determined for the standard solutions of lutein. However, the influence of lutein on the RSA values of spinach and kale is relatively low. Spinach, more than other analysed plants had an exceptionally high total polyphenol and flavonoid content.