Following alcohol, marijuana is the second most popular drug with youth. It consists of the leaves, flowers, stems, and seeds of the cannabis plant, which are dried and chopped into small amounts. Marijuana can also be found as Sinsemilla, the potent flowering tops of the female marijuana plant.

Commonly referred to as grass, pot, weed, Acapulco Gold, ganja, and smoke, marijuana is usually sold and stored in small plastic bags, aluminum foil, or small rolled cigarettes. Marijuana is usually smoked in hand-rolled cigarettes called "joints," and has a strong, pungent odor when smoked. Once the marijuana cigarette is partially smoked, it is often held by a small clip called a "roach clip." (Roach clips are made from many items, such as tweezers or electrical clips.)  The leaves can also be smoked in small wooden pipes or water-filled pipes called "bongs." And finally, marijuana can also be blended into food, then cooked and eaten, most often in brownies.

Paraphernalia associated with marijuana includes pipes, bags, rolling papers, plastic bags, roach clips, "stash boxes" (decorative boxes designed to conceal and store marijuana), and eye drops and breath fresheners used to cover up signs of use of the drug.

In low doses, marijuana can induce restlessness, a dreamy state of relaxation, red or bloodshot eyes, and increased appetite. Stronger doses can cause shifting sensory images, rapidly fluctuating emotions, a loss of self-identity, fantasies, and hallucinations or image distortions.