Objective: Opioids are effective in cancer pain management but their use is frequently complicated by side effects such as constipation. The aim of the study was to assess opioid-induced constipation (OIC) in a sample of palliative care cancer patients under treatment with WHO step III oral opioids. A secondary aim was to describe laxative medication use in the same sample. Method: This was a prospective, observational study of 14-day duration. Subjects with a documented history of cancer pain in treatment with around-the clock oral strong opioids were eligible to participate in the study. Results: The analysis included 97 patients (mean age 76.0 ± 10.1): 50 were under treatment with oxycodone/naloxone, 25 with morphine, 20 with oxycodone and 2 with hydromorphone. The mean BFI was 35.67 ± 19.38 at recruitment and there were no significant modifications within the 14 days of study. The percentage of non-constipated patients (BFI <28.8) was higher in the OXN group than in the other groups, at both T1 (7 days after recruitment) and T2 (14 days after recruitment) (p<0.05). During the study period 46.4% of patients were under treatment with laxative medications. Patients in treatment with oxycodone and morphine consumed more laxatives than the OXN (chi-square 11.30, p-value 0.0007). 87.4% patients referred laxatives AEs. Conclusions: The study was limited due to difficult advanced cancer patients’ recruitment. However this work reinforces the need of further research in palliative care to pro¬vide evidence-based guidance on OIC management in this population.