AIMS: This prospective, cross-sectional study aimed to assess cancer pain and its management in an inpatient setting at a comprehensive cancer centre in Denmark. METHODS: One hundred and eighty-eight inpatients with cancer were invited to participate (May/June 2011). Demographics, diagnoses, World Health Organization performance status, health-related quality of life, pain and data regarding analgesic treatment were registered. RESULTS: One hundred and thirty-four (71.3%) patients agreed to participate in the study. Most frequent diagnoses were leukaemia (27.6%) and lung cancer (14.2%). A high prevalence of pain was observed, 65.7%. Thirty-two per cent reported moderate to severe pain when it was at its worst, 96% reported no or mild pain when it was at its least. Nearly 22% reported moderate to severe pain when the pain was categorised as average. Breakthrough pain episodes were reported by 30.5%. Adjuvant medication was sparsely used and not always correctly indicated. Out of 88 patients with pain, 62.5% were left untreated according to the Electronic Medication System. Higher health-related quality of life was associated with lower pain intensity. The use of opioids with or without adjuvants was associated with higher pain intensity and higher number of breakthrough pain episodes. CONCLUSIONS: Approximately two thirds of inpatients reported pain and one third had breakthrough pain. A substantial number of patients with pain were left untreated. Opioid-treated patients reported highest pain intensity and number of breakthrough episodes; however, analgesic medication seemed to be underused. Measures to improve pain assessment and management are highly required.