As for other aromatic plants, there are many analytical methods for the determination of volatile compounds in lavender essential oils. Alternatively, in this study RP-HPLC-DAD-QTOF-MS was used for the profiling of the phytochemical constituents of hydromethanolic extracts of L. stoechas and L. dentata, which were obtained by pressurized liquid extraction. The spectrometric data revealed complex profiles constituted of a wide range of polar and semi-polar phytochemicals, mainly, phenolic compounds (68). Most phenolic compounds (55) have not been previously reported in Lavandula; such is the case of caffeic acid-based oligomers. Moreover, the analytical method was validated for the determination of phenolic compounds. Our findings showed both qualitative and quantitative differences between the extracts. In this sense, while hydroxycinnamic acids made up the largest class in both extracts, flavones were the most abundant class, accounting for 10.44g (L. dentata) and 4.85g (L. stoechas) per 100g of dry extract. In conclusion, this analytical method provided essential information about the phytochemical composition of the studied medicinal plants, revealing novel constituents that were probably hidden for others. In addition, these results may help to understand the anti-inflammatory properties of these extracts.