Cannabis sativa L has a long history as a medicinal plant, dating back more than two millennia. Preclinical studies using both pharmacological and genetic approaches have increased the understanding of this plant and its importance in providing therapeutic strategies for a variety of conditions. The cannabis plant comprises hundreds of different active compounds with potential therapeutic properties, with cannabinoids being the main class of active compounds. Recent drug development has produced cannabinoid-rich cannabis-based medicinal products, which were legalised in November 2018 in the UK. They are increasingly prescribed for conditions, including multiple sclerosis, epilepsy and chronic pain. This article aims to review the current literature on the therapeutic effects and applications of the two main cannabinoids found in cannabis-based medicinal products.