Introduction Fennel (Foeniculum vulgare Mill.) and basil (Ocimum basilicum L.) are two aromatic medicinal plants. Recently, a new parting process which is named CDS “Comminution and to control Diffraction Sieving” is taken into consideration and its positive effect on the extraction of bioactive compounds from the plants, without any solvent, is reported. Objective Study the effect of CDS on phytochemical properties of superfine powders of fennel seeds and basil leaves. Methods Fennel seeds and basil leaves superfine powders were fractionated as follows: 100–180 μm, 180–315 μm, 315–500 μm, > 500 μm and unsieved superfine powders. Extraction of polyphenols was carried out using hydromethanolic maceration. The essential oils were extracted by maceration with dichloromethane. The antioxidant activities were evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Using liquid chromatography ultraviolet electrospray ionisation mass spectrometry (LC-UV-ESI-MS), concentrations of characterised phenolic compounds were measured. The essential oils compositions were characterised using gas chromatography mass spectrometry (GC–MS). Results In fennel seeds, the 100–180 μm fraction had maximum antioxidant activity and LC-UV-ESI-MS analyses proved that the best extraction of certain polyphenols was obtained in the 100–180 μm fraction. In basil leaves, the best antioxidant activity corresponded to the 315–500 μm fraction and LC-UV-ESI-MS analyses showed that the polyphenols were concentrated in the < 315 μm fractions. For both plants, GC–MS presented that the essential oils were concentrated in the 315–500 μm fraction. Conclusion CDS as a new green parting process leads to improve the phytochemical properties of these two superfine plant powders in the specific granulometric classes.