Background: Life quality evaluation is the main indicator of the impact of palliative care, which has the objective of diminished suffering. It includes symptoms control and the satisfactions of patients and relatives. Opioids constitute a milestone in pain treatment. Present work is aimed to evaluate the secondary effects in oncological patients with bad prognosis treated with morphine at the Palliative Care Unit (PCU) of the National institute of Oncology and Radiobiology. Methods: The sample includes 72 cancer patients that arrive to the Palliative Care Unit of the National Institute of Oncology and Radiobiology of Cuba, from May 2015 to May 2016. It was characterized in terms of the demographic and clinical parameters. Severity of symptoms was evaluated using the Visual Analogue Scale (VAS). Pain was evaluated using Analogue Visual Scale. Morphine was administered subcutaneously. Incidence of adverse effects related to morphine administration and accuracy of moderate to severe pain was measured. Results: The age range was from 41 to 50 and females predominate. Gynecological cancers were the most frequent pathology. Most frequent adverse effects related to morphine administration were: constipation (35%), nauseas and vomiting (25%) and somnolence (22%). Despite of morphine myths that terrify many physicians and make them use this drug at the end of analgesic scale, in the present work was used in patients in clinical stage III (58.6 % of the 63.8 % survivors) with an effective pain control. Life quality, that includes mood, functional capacity, social interaction and recurrent symptoms, was improved. Conclusions: The use of morphine for pain relief in stage III oncological patients increases the quality of life of patients and relatives for a longer period of time.