Mind-mindedness (MM) refers to the parent's ability to treat the child as an individual with a mind of his or her own. Studies have found representational and interactional MM to predict child development, but more research is needed on the validity of representational MM in parents of infants. Therefore, we examine the reliability and validity of representational MM in 46 mothers of infants. Representational MM was measured at 4 and 11 months, and interactional MM at 11 months. The results supported the reliability of representational MM by showing a moderate rank-order stability over a 7-month-period, although the stability was due to associations between representational MM and maternal age. The results also supported the validity of representational MM by showing concurrent and longitudinal associations between representational and interactional MM. Finally, the results suggested that the capacity for appropriate mind-related comments is more stable than the tendency to use non-attuned mind-related comments.