The consumption of Citrus fruits and juices has been widely investigated for its possible role in the prevention of cardiovascular disease and cancer. These beneficial effects are mainly attributed to flavanones, the typical polyphenols of Citrus species. Major flavanones in plant species include hesperetin, naringenin, eriodictyol, isosakuranetin and their respective glycosides. Hesperetin and its derivatives are characteristic flavanones of sweet orange, tangelo, lemon and lime, while naringenin and its derivatives are those of grapefruit and sour orange. Advances in analytical techniques like ultra high performance liquid chromatography (UPLC) coupled with mass spectrometry has facilitated (a) the estimation of flavanone contents in other plant species and in humans after ingestion and (b) the determination of flavanone metabolites more rapidly and with greater efficiency. The present review will summarize the current knowledge about flavanones from their occurrence in plants to the bioactivity of their metabolites in humans.