Objective To examine the relationship of external influence to parental distress when making a decision about research or treatment for a child with a life-threatening illness and to test potential moderators of this relationship. Methods Parents (n = 219) who made a decision about research or treatment for a child completed measures of external influence, distress, decision-making preference, and coping. Results More external influence was associated with more hostility, uncertainty, and confusion. Decision-making preference and coping style moderated the relationship between external influence and distress: More external influence was associated with more distress when decision-making preference was low and task-focused coping was high. Conclusions External influence appears to be related to distress in parents making research and treatment decisions for children with life-threatening illnesses. However, it is important to consider parent characteristics, such as decision-making preference and coping style, when examining the effects of contextual factors on distress during decision making.