With the increasing intake of flavonoids in diet, supplements and herbal medicines, studies on the biotransformation and disposition have been dramatically expanded. The current review covers the findings on the relationships between flavonoid structural properties and their glucuronidation activities in in vivo trials and in vitro human UGTs or microsomes for the past 2 decades. Regioselectivity and substrate specificity on the glucuronidation of flavonoids are summarized. The findings reveal the inconsistency from different studies and indicate the importance of in silico modeling in the prediction of structure-glucuronidation relationship.