Marijuana (cannabis) remains a controversial drug in the 21st century, even though the plant has been known to human beings for at least 10, 000 years with hemp-woven clothing material recorded in ancient China in 8, 000 BCE and hemp foods in ancient China in 6000 BCE. It has been used for cancer pain, neuropathic pain and spasticity with multiple sclerosis, and other indications such as chronic pain and also in epilepsy management and current research is evaluating the anti-epileptic role. The potential role of specific cannabinoids for medical benefit will be revealed as the 21st century matures. However, potential dangerous adverse effects from smoking marijuana are well known and should be clearly taught to a public often confused by a media-driven, though false message and promise of benign pot consumption. In this book we will review not only cannabis, but pain and disorders causing pain in children and adolescents.