Cannabis is the only plant to contain Cannabinoids. In the future, with the development of gene-splicing and genetic engineering, it may be possible to 'design' other plants to produce these psychoactive cannabinoids. Almost 40 cannabinoids have been discovered and isolated. But most of them are not psychoactive, just six and they are:

Delta 9-Tetrahydracannabinol is the principal psychoactive ingredient. All cannabis contains at least some Delta 9-THC, although Industrial Hemp will contain only minute traces. Most Cannabis grown for the Marijuana will contain more, some cannabis plants weighing in at 25% Delta 9-THC.
Delta 8-THC can also be found, but usually in very low concentrations, so most breeders and researchers ignore this compound and concentrate on the more abundant and potent Delta 9-THC.

Cannabidiol, also known as CBD, appears in virtually all forms of cannabis; though the amounts vary from a trace to 95% of the plant. CBD is the compound found to give the sedative effect to the 'high' experienced.
CBD, it is also found, has the tendency to delay the 'high', but also to prolong the 'high'.
Whether CBD increases or decreases the force of the 'high', depends on the individual cannabis smoker.

Cannabinol, or CBN is produced as THC oxidises or degrades. Only a trace amount appears in fresh buds, but stored or cured (dried) buds and Hashish tends to have higher amounts of CBN because the THC had degraded in the process of preparing the buds and the making of Hashish. CBN has been found to be the compound that gives the cannabis smoker a disoriented, sleepy or groggy effect. This is referred to as a 'stupefying high'. At best, CBN contains only 10% of the psychoactive effect of the original Delta 9-THC.

THCV, or Tetrahydrocannabivarin, is the compound associated with the fragrance of the cannabis plants. Very pungent smelling cannabis plants usually contain high amounts of THCV. It is also found in very potent marijuana that originates in southeast and central Asia, as well as regions of Africa. These high concentrations of THCV will make the 'high' come on quicker but last for less time.

Cannabichromene, or CBC makes up to 20% of the cannabinoid compound of the cannabis plant. Though little research has been done, scientists and professional breeders think that CBC might interact with THC to make for a more intense 'high'.