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This paper describes the process followed to create and validate the Portuguese versión of a quality of life measurement instrument for patients in palliative care. After a literature review about the measurement of the quality of life in this particular and very specific kind of patients, we opt by the Irene Higginson's measurement instrument called Palliative Care Outcome Scale (POS). It has been selected as the one most appropriate to Portuguese patients' reality. For the creation of the Portuguese version we followed the recommended methodologies for the forward-backward translations. These methodologies allow us to determine semantic and linguistic equivalences of health outcomes measurement instruments. The validation was performed on a sample of 104 cancer patients aged between 40 and 85 years old. 70% were female, 29% had lung cancer, 46% breast cáncer and 22% had melanoma. Content validity was assured by two cognitive debriefing tests, respectively performed in oncologists and in patients. Construct validation allow us to find five ortogonal factors, including 'emotional well being' (19.7% of variance explained), 'consequences of the disease in life' (18.2%), 'received information and support' (11.7%), 'anxiety' (10.1%), and 'burden of illness' (9.8%). Criterion validity was tested by comparing the results obtained by POS to the ones obtained by the EORTC QLQ-C30, a genetic instrument especially designed for cancer patients. The found correlation values were moderated to strong and ranged from 0.51 to 0.63. The reliability of the Portuguese version was assured through the reproducibility test and the search for the internal consistency. The scores obtained by a one-week testrestest ranged from 0.66 to 1.00. Cronbach's alpha was 0.68, acceptable and allowing us to consider POS as a unique index Time responsiveness and diagnosis responsiveness were also analysed. Comparing values measured with a one-month interval showed sensibility to the lack of the quality of life felt by patients. This measurement instrument was also sensitive to the various pathologies. In conclusion, we may defend the quality of the performance of the Portuguese versión of the POS. This version may be used to prospectively assess the palliative care on advances cancer patients.