The aim of this study was to 1) assess cancer patients' share in a population's use of opioids and how much it influences the total use, and 2) analyze trends in the population's use of "weak" and "strong" opioids during a five-year period. Person-identifiable data on opioid prescriptions and cancer diagnoses from a Danish county (n approximately 470,000) were retrieved from a prescription database, OPED, and The Danish Cancer Registry from 1993-1997 (identifying 23,843 cancer patients). In a given year, 14% of the population's opioid users were cancer patients, and they received 23% of the total opioid consumption. Over time, the number of patients using weak opioids increased and the number using strong opioids decreased among both cancer patients and non-cancer patients. Cancer patients' consumption of strong opioids increased dramatically in 1996-1997, almost accounting for the entire increase in the whole population's consumption of strong opioids.