Levels of personal control exercised by 76 adults with mental retardation were contrasted by substitute decision-making status. Individuals with no guardian or conservator exercised more personal control than did those with a conservator, who exerted more personal control than did participants with a guardian. Similar group differences in self-determination competencies were also observed. When self-determination competencies were controlled statistically, significant group differences in exercise of personal control remained. Restrictive substitute decision-making status, inappropriate to current competencies, may have constrained individuals' levels of personal control. Reviewing substitute decision-making status on a regular basis and limiting or removing guardianship/conservatorship when it is not appropriate, may enhance personal control.