delta 9-Tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN) are three constituents of the 16 that can be currently isolated from some Cannabis spp plants. Their identification in decontaminated hair can indicate exposure to cannabis. In this study, we propose a rapid, simple, and direct (without derivatization) screening procedure for the simultaneous identification and quantitation of CBD, CBN, and THC in hair of chronic cannabis abusers. Hair samples were washed with methylene chloride, hydrolyzed with sodium hydroxide, extracted with n-hexane-ethyl acetate (9:1, v/v), evaporated to dryness, and injected directly on a gas chromatographic-mass spectrometric system operating in electron-impact mode. THC-d3 was used as the internal standard. Thirty hair samples were tested. CBD was detected 23 times, CBN was detected 22 times, and THC was detected five times. Concentrations ranged from 0.03 to 3.00 ng/mg (mean, 0.44 ng/mg), from 0.01 to 1.07 ng/mg (mean, 0.13 ng/mg), and from 0.1 to 0.29 ng/mg hair (mean, 0.15 ng/mg) for CBD, CBN, and THC, respectively. These results show that this new screening procedure is suitable for the detection of CBD and CBN in the hair of cannabis abusers.