A compound for use in a method of treating a mitochondrial disorder, a compound that is selected from the group consisting of: (a) compounds of formula XO, formula XR, formula XII-O and formula XII-R: ** Formula ** where R11, R12 and R13 are independently selected from the group consisting of H, -C1-C4 alkyl, -C1-C4 haloalkyl, -CN, -F, -Cl, -Br and -I, with the proviso that if any of R11, R12 or R13 is H, then at least one of the other two substituents is not H or methyl； and all stereoisomers, mixtures of stereoisomers, solvates and hydrates thereof； and (b) compounds of formula VII-O, formula VII-R, formula IX-O and formula IX-R: ** Formula ** where R1, R2 and R3 are independently selected from -C1-C4 alkyl, with the provided that at least one of R1, R2 and R3 is not methyl； and all stereoisomers, mixtures of stereoisomers, solvates and hydrates thereof； wherein the method comprises administering a therapeutically effective amount of the compound； and in which the mitochondrial disorder is selected from the group consisting of Leber's hereditary optic neuropathy (NOHL)； Leigh's disease； mitochondrial myopathy, encephalopathy, lactic acidosis, stroke (MELAS)； Kearns-Sayre syndrome (SKS)； Friedreich's ataxia (AF)； hereditary mitochondrial diseases； myoclonic epilepsy associated with torn red fibers (RRMS)； other myopathies； cardiomyopathy； encephalomyopathy； renal tubular acidosis； neurodegenerative diseases； Parkinson's disease； Alzheimer disease； Amyotrophic lateral sclerosis (ALS)； neuromotor diseases； other neurological diseases； epilepsy； genetic diseases； Huntington's disease； mood disorders； schizophrenia； Bipolar disorder； age-related diseases； macular degeneration； and diabetesUn compuesto para su uso en un método para tratar un trastorno mitocondrial, compuesto que se selecciona del grupo que consiste en: (a) compuestos de fórmula X-O, fórmula X-R, fórmula XII-O y fórmula XII-R: **Fórmula** donde R11, R12 y R13 se seleccionan independientemente del grupo q
