The seed extracts of olive tree cultivars were analyzed by reverse phase HPLC with diode array detection and mass spectrometry. HPLC hyphenation with mass spectrometry (ESI source) in both polarity modes enabled the identification in olive seeds of nuzhenide and nuzhenide 11-methyl oleoside, among other 11-methyl oleosides, by means of MSn. The methods used allowed us to obtain olive seed profiles of phenolic components and to conclude that they are mainly secoiridoids. The quantification of detected phenolic secoiridoids was also achieved using ultraviolet detection (lambda = 240 nm) which enabled comparison of the samples. Nuzhenide and nuzhenide 11-methyl oleoside were the major components detected in olive seeds of all the cultivars studied, but variations in individual components of olive seeds were verified among the cultivars. The results also support the existence of di and tri(11-methyl oleosides) of nuzhenide.