Inclusion Criteria:

• Patients who are currently receiving strong opioid analgesic for their cancer pain management
• Patients who are able, in the opinion of investigator, to comply fully with the trial requirements including completion of the Korean-Brief Pain Inventory
• Patients who have signed an informed consent form

Exclusion Criteria:

• Patients with pain that was not considered to be potentially responsive to opioids
• A recent (within the past 6 months) or currently history of drug and/or alcohol abuse
• Women of childbearing potential who are pregnant or lactating, seeking pregnancy, or failing to take adequate contraceptive precautions
• Patients with an intolerant of, or hypersensitivity to, hydromorphone or other opioids
• Patients with GI disease of sufficient severity to be likely to interfere with oral analgesia including: dysphagia, vomiting, no bowel movement or bowel obstruction due to impaction within 5 days of the study, severe gut narrowing or factors predisposing to gut narrowing (both hereditary or iatrogenic [e.g. GI surgery or GI radiotiotherapy]) that may affect the absorption or transit of orally administered drugs, particularly the insoluble OROS outer coating
• Patients who were receiving or had received monoamine oxidase inhibitors (MAOIs) within the past 2 weeks
• Patients who had previously enrolled in this trial
• Patients who had participate in another trial with an investigational drug in the last 4 weeks
• Patients in whom the risks of treatment with morphine/hydromorphone outweighed the potential benefits, including such risk categories as raised intracranial pressure, hypotension, hypothyroidism, asthma, reduced respiratory reserve, prostatic hypertrophy, hepatic impairment, renal impairment, elderly and debilitated, convulsive disorders, and Addison's disease