Cancer patients suffer in part because some health professionals prescribe or administer amounts of analgesics, namely opioids, which are too small or too widely spaced to be fully effective. Patients' reluctance to use opioids for pain treatment is often mentioned as a reason not to apply the official guidelines, but very few studies have been conducted on people's attitudes about opioid use to relieve cancer pain. One hundred twenty lay participants and 30 health professionals (7 physicians and 23 nurses) were presented with a set of vignettes describing a terminally ill woman with cancer who is in pain. The vignettes were composed according to a four within-subject factor design: (a) level of pain reported by the patient, (b) patient's explicit request for additional administration of analgesics, (c) the physicians' final decision (e.g., to use a stronger analgesic combining paracetamol and codeine), and (d) the way the decision was made (collectively or not). Participants were asked to assess the extent to which the physician's decision was, in their view, acceptable. Seven qualitatively different positions were found among participants. They were called as follows: tend to disagree with any decision (9%), increase the strength of the painkiller in any case (16%), give morphine preferentially (9%), partly depends on pain level (23%), fully depends on pain level (6%), depends on decision process and on pain level (22%), and tend not to disagree with any collective decision (25%). Overall, 91% of participants agreed with the use of morphine in terminally ill cancer patients when the pain level was high (score of 7) and the decision to increase the strength of the painkiller was taken collectively. This percentage dropped to 69% when the team was not involved in the decision and to 40% when the pain level was lower (score of 4). If opposition to the use of morphine exists, it is not opposition to morphine itself but opposition to the circumstances of its use.