In the current study, phenolic compounds of the tomato (Solanum lycopersicum) skin extract were separated and their composition was determined by capillary electrophoresis and tandem high-performance liquid chromatography diode array detection-mass spectrometry (HPLC-DAD-MS/MS). Both the total phenolic and flavonoid contents of the extract were determined. The antioxidative capability of the extract was measured using a stable free radical 2,2-diphenyl-1-picrylhydrazyl assay. The monitoring of the radical scavenging capability of specific phenolic compounds was carried out both by capillary electrophoresis and HPLC-MS/MS.