Nowadays, Gas Chromatography Mass Spectrometry (GC-MS) is mainly used in forensic sciences but suffers from limitations when the analysed compounds are thermally instable as it is the case for THC-A (Tetrahydrocannabinolic Acid) which is converted into Δ9-THC (Δ9-Tetrahydrocannabinol) that subsequently partially degrades. We propose herein a Fast High Pressure Liquid Chromatography (Fast-HPLC-DAD) method which allows the efficient separation of CBN (Cannabinol), CBD (Cannabidiol), THC-A and Δ9-THC, the major cannabinoids compounds found in cannabis plants in less than 5 min. Our method allows also the proper quantification of Δ9-THC in plant extracts using an external calibration method with a very good accuracy as pointed out by a recovery of 100.53 ± 3.12%. It is also an interesting low cost alternative to Ultra High Pressure Liquid Chromatography (UPLC) for routine analyses in forensic sciences.