This study examined (a) how physicians and nurses in France and Quebec make decisions about life-sustaining therapies (LSTs) for critically ill children and (b) corresponding ethical challenges. A focus groups design was used. A total of 21 physicians and 24 nurses participated (plus 9 physicians and 13 nurses from a prior secondary analysis). Principal differences related to roles: French participants regarded physicians as responsible for LST decisions, whereas Quebec participants recognized parents as formal decision-makers. Physicians stated they welcomed nurses’ input but found they often did not participate, while nurses said they wanted to contribute but felt excluded. The LST limitations were based on conditions resulting in long-term consequences, irreversibility, continued deterioration, inability to engage in relationships and loss of autonomy. Ethical challenges related to: the fear of making errors in the face of uncertainty; struggling with patient/family consequences of one’s actions; questioning the parental role and dealing with relational difficulties between physicians and nurses.