The success of opioid treatment in terminally ill cancer patients set the stage for extending the same treatment principles to the treatment of all chronic pain conditions including chronic non-cancer pain and chronic pain in cancer, where survival and long-standing chronic disease trajectories are getting more prevalent due to increasing survival rates. In this context, opioid misuse as such has been highly neglected - especially in palliative care, but also in cancer pain management in general. Previous studies have explored the literature on opioid misuse among adult cancer patients, noting that the available evidence is still in its early stages. Limited prospective studies with a wide range of definitions and methodologies for assessing misuse exist. Therefore, it seems highly relevant and justified to study the prevalence of opioid misuse risk in patients with cancer. The hypothesis of this study is that opioid misuse is not uncommon in Danish patients in treatment with opioids for cancer-related pain. Thus, the prevalence of opioid misuse risk among patients with cancer in Danish palliative care units will be investigate.