The constituents of Korean cannabis were studied comparatively with foreign orgins. Especially, tetrahydrocannabinol(THC), the active constituents of cannabis were analyzed by the technique of thin layer chromatography and colorimetry. The results are as follows ; (1) THC content in Korean cannabis is comparatively higher than that in foreign samples. (2) THC is contained most abundantly in male flowers, abundantly in female tops and leaves and some in barks. (3) There is a tendency that the THC content increase gradually with growth of plants, being highest during unripe nad decrease with maturity of the tops. (4) Korean cannabis contains THC, cannabinol, cannabidiol, cannabidiolic acid and other cannandiolic compounds. Distribution of chemical components of Korean cannabis, compared with those of foreign ones, is remarkably different. (5) The THC content of Spanish cannabis cultivated tentatively in Korea is similar to that of Korean cannabis.