This is the first report of chemiluminescence from the reaction of cannabinoids with acidic potassium permanganate, which we have applied to the high performance liquid chromatography (HPLC) determination of cannabidiol (CBD) in industrial-grade hemp. The intensities of the light-producing reactions with two commercially available cannabinoid standards were compared to that of seven model phenolic analytes. Resorcinol, representing the parent phenolic moiety of the cannabinoid class, was shown to react with the permanganate reagents in a manner more similar to phenol than to its hydroxyphenol positional isomers, pyrocatechol and hydroquinone. Alkyl substituents on the phenolic ring, however, have a considerable impact on emission intensity that is dependent upon the position of the groups and the composition of the permanganate reagent. This analytical approach has potential for the determination of other cannabinoids including Δ(9) -tetrahydrocannabinol in drug-grade cannabis.