Published studies suggested an implication of oxytocin in some temperament characteristics of personality. Therefore, we measured oxytocin secretion in 23 women with anorexia nervosa (AN), 27 with bulimia nervosa (BN) and 19 healthy controls and explored the relationships between circulating oxytocin and patients' personality traits. Plasma oxytocin levels were significantly reduced in AN women but not in BN ones. In healthy women, the attachment subscale scores of the reward dependence temperament and the harm avoidance (HA) scores explained 82% of the variability in circulating oxytocin. In BN patients, plasma oxytocin resulted to be negatively correlated with HA, whereas no significant correlations emerged in AN patients. These findings confirm a dysregulation of oxytocin production in AN but not in BN and show, for the first time, a disruption of the associations between hormone levels and patients' temperament traits, which may have a role in certain deranged behaviours of eating disorder patients. Copyright © 2015 John Wiley & Sons, Ltd and Eating Disorders Association.