Medicinal plants have been used since the existence of mankind. Herbal medicines based on traditional medicine endure as primary health care delivery worldwide up today. In addition, natural compounds have been used as either conventional drugs or inspiration model for synthetic drugs. Plants are still good sources for discovering new compounds with therapeutic potential. Diterpenoids, comprising a varied group of secondary metabolites, are isoprene derived compounds consisting of four isoprene units. Diterpenes are classified mainly according to their chemical structure, in terms of the ring number they contain as: acyclic (phytane), monocyclic (retinol—vitamin A), bicyclic (labdane, halimane, clerodane), tricyclic (abietane, pimarane, cassane, rosane, podocarpane, chinane, vouacapane), tetracyclic (kaurane, trachylobane, aphidicolane, stemodane, stemarane, beyerane, atisane, scopadulane, gibberellane), and macrocyclic (polycyclic—cembrane, taxane, daphnane, tigliane, ingenane, jatrophane), and other miscellaneous structures. Diterpenes are mainly analyzed by liquid chromatography coupled with high-resolution mass spectrometry; tandem mass spectrometry; diode array detection depending to the structure. Ultra-high-performance liquid chromatography tandem mass spectrometry method and gas chromatography-mass spectrometry also can be applied. Natural foods may contain terpenoids, diterpenes, and tetraterpenes as secondary metabolites. Diterpenes have been used in traditional medicine for anticancer, antidiabetic and various other ailments. In this chapter, properties and classification of diterpenes, importance of chromatography in diterpenes analysis, effects of processing in the phytochemicals have been discussed.