The delta9-tetrahydrocannabinol (delta9-THC) content was identified and determined quantitatively using a Gas Chromatography Detector (Gas Chromatography-Electron Ion Detector) instrument in samples of illicit herbal cannabis. Law enforcement authorities sent the samples to the Department of Forensic Medicine and Toxicology, University of Athens, for toxicological analysis. The concentrations of delta9-THC in these samples ranged from 0.08% to 4.41%. Such concentrations suggest that Greece might be at high risk, as an area for the illicit cultivation of "pedigree" cannabis plants. The forensic aspects of cannabis classification are discussed.