Background: During adolescence diabetes creates a juncture of very complex disease management demands with developmental needs, including the striving of adolescents for greater autonomy. Parents' concerns and fears about the teen's diabetes self-management abilities during this time can heighten parental attachment behaviour and affect the parents' ability to support autonomy development necessary for effective self-care. Maternal parenting processes may be especially important for those adolescents who have Type 1 diabetes because mothers are the primary caregivers. Purpose: Based on attachment theory, the aim was to test a model of the influence of mother-adolescent developmental conflict, maternal separation anxiety and maternal inhibition of autonomy and relatedness on cognitive autonomy and self-care of adolescents with Type 1 diabetes. Method: A total of 131 families with an adolescent, aged 11-15 years, contributed data annually across three waves. Mothers and adolescents completed paper-and-pencil measures and two interaction scenarios that were coded by trained staff from audio-tapes. The adolescent also completed a structured interview and questionnaire to assess self-care. Results: Maternal separation anxiety when adolescents were 11-15 years of age directly predicted cognitive autonomy at 1-year follow-up, and that cognitive autonomy was directly related to self-care 1 year later, but did not mediate between separation anxiety and self-care. Conclusions: Future investigation of the influence of separation anxiety of parents on adolescent autonomy development is warranted, as well as the contribution of autonomy development to diabetes self-management behaviours of adolescents. © 2009 Blackwell Publishing Ltd.