Coenzyme Q₁₀(CoQ₁₀) in human milk at different stages of maturity in mothers of preterm and full-term infants and its relation to the total antioxidant capacity of milk is described for the first time. Thirty healthy breastfeeding women provided colostrum, transition-milk and mature-milk samples. Coenzyme Q, α-, γ- and δ-tocopherol, fatty acids and the total antioxidant capacity of the milk were analyzed. Coenzyme Q₁₀ was found at higher concentrations for colostrum (0.81 � 0.06 vs. 0.50 � 0.05 μmol/l) and transition milk (0.75 � 0.06 vs. 0.45 � 0.05 μmol/l) in the full-term vs. the preterm group (similar results were found for total antioxidant capacity). Concentrations of α- and γ-tocopherol were higher in the full-term group and decreased with time. In conclusion, CoQ₁₀ is present in breast milk, with higher concentration in mothers of full-term infants. CoQ₁₀ in breast milk decreases through lactation in mothers delivering full-term infants. Also, CoQ₁₀, α- and γ-tocopherol concentration in human milk directly correlates with the antioxidant capacity of the milk.