Coenzyme Q10 (CoQ10), also known as ubiquinone, is a fat-soluble vitamin-like molecule that is synthesized endogenously and is found in the inner membrane of mitochondria of many cells. Optimal endogenous CoQ10 synthesis occurs up to the age of 20 years [Kalén A, Appelkvist EL, Dallner G. Age-related changes in the lipid compositions of rat and human tissues. Lipids. 1989;24:579–84] and then concentrations appear to decline with age, so there is limited rationale for CoQ10 supplementation in otherwise healthy children. A small amount of CoQ10 is also obtained from the diet (meat, fish, and nuts). CoQ10 is crucial for efficiently transferring electrons within the mitochondrial oxidative respiratory chain and producing adenosine triphosphate (ATP) for energy production. In its reduced form, ubiquinol plays an important role as antioxidant in lipid structures, such as cellular membranes and lipoproteins, protecting these from damaging oxidative processes. Due to its essential role in mitochondrial energy production, it affects the function of all cells, especially those with high energy demands such as the heart, kidneys, muscles, and brain.