Cyclic vomiting syndrome (CVS) is a functional gastrointestinal disorder characterized by recurrent stereotypic episodes of vomiting. The pathophysiology of CVS remains obscure. Previous studies have supported the hypotheses of mitochondrial dysfunction. However, data on association studies between mitochondrial DNA (mtDNA) polymorphisms and pediatric-onset CVS are limited and inconsistent. The aims of this study were to describe clinical characteristics, evaluate association of mtDNA polymorphisms 16519T and 3010A with pediatric-onset CVS and identify new mtDNA candidate variants.