The prevalence of cancer-related pain is high despite available guidelines for the effective assessment and management of that pain. Barriers to the use of opioid analgesics partially cause undertreatment of cancer pain. The aim of this study was to compare pain management outcomes and patient-related barriers to cancer pain management in patient samples from Denmark and Lithuania. Thirty-three Danish and 30 Lithuanian patients responded to, respectively, Danish and Lithuanian versions of the Brief Pain Inventory pain scale, the Barriers Questionnaire II, the Hospital Anxiety and Depression Scale, the Specific Questionnaire On Pain Communication, and the Medication Adherence Report Scale. Emotional distress and patient attitudes toward opioid analgesics in cancer patient samples from both countries explained pain management outcomes in the multivariate regression models. Pain relief and pain medication adherence were better in Denmark, and the country of origin significantly explained the difference in the regression models for these outcomes. In conclusion, interventions in emotional distress and patient attitudes toward opioid analgesics may result in better pain management outcomes generally, whereas poor adherence to pain medication and poor pain relief appear to be more country-specific problems.