Inclusion Criteria: - Patients who complain of cancer pain and who require administration of hydromorphone HCl - Patients who can follow the requirements of the overall study, including completion of filling out the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, at the investigator's discretion - Signed informed consent Exclusion Criteria: - Patients who received strong continuous narcotic analgesics (eg morphine, fentanyl, oxycodone, hydromorphone) within 4 weeks prior to administration of the study drug - Patients who have a medical history of receiving drugs in the past or currently, or of drug abuse - Patients who did not agree to conduct the approved methods for contraception during the study - Patients who have sustained injuries in physical functions or diseases which may cause abnormalities in absorbing the study drug, excessive accumulation and metabolic or elimination disorder - Patients who are receiving Monoamine Oxidase Inhibitors (MAO) inhibitors or who are within 2 weeks from discontinuation - Patients who need to be excluded based on precautions in the user manual of the study drug, notice and contradictions, at the investigator's discretion