Researchers from the University of Glasgow who followed the progress of patients at 25 hospitals across Scotland found 28.8% died within a year.
The study, carried out with a view to informing end-of-life care strategies in hospital, examined the age, health and treatment of patients on one day.
Of the patients involved, 2.9% died within a week, 16% within three months and 25.5% within nine months. The study found men were more likely to die than women, as were patients over 85 compared to those under 60.
Professor David Clark, head of the school of interdisciplinary studies at the university, said that the research showed there was a need for hospitals to adopt a more vigorous approach to identifying patients who are entering the last year of their lives.
One study last year covering 36 nations ranked Scotland 12th highest for the proportion of all deaths in hospital (59%) with Japan (78%) having the highest proportion of hospital deaths.
The report, co-authored by Mr Clark, said: "This study supports clinicians and managers to give greater priority to the identification of patients at the end of life and to encourage a more proactive response to their needs."
The authors believe the study of patients in March 2010, was the first of its kind to establish the proportion of hospital in-patients that die over a period of 12 months from a given date, and how the likelihood of death is related to gender and age.
Age Scotland was worried about the results of an "impressive piece of large-scale research which is very valuable to giving us robust data in this area where data has been an issue".
Age Scotland chief executive Brian Sloan said: "These findings reinforce the need to ensure all healthcare staff are appropriately trained to both identify those who have palliative care needs, and to then have the confidence and skill to broach the subject with patients and families.
"Too many people, particularly non-cancer patients, are not being identified for palliative care early enough and they, and their loved ones, are therefore missing out on vital support which can have a devastating impact on families."
A Scottish Government spokesperson said: "Living and Dying Well, our national action plan on palliative and end of life care, emphasises the importance of early identification of people with palliative care needs. However, it must be recognised that there are often considerable challenges associated with identifying patients who are entering their final year of life.
"The Scottish Government remains committed to delivering high quality palliative and end of life care in Scotland. Working together with our key stakeholders we have made great progress in the provision of palliative care. However, we are not complacent, and are now developing our Strategic Framework for Action which will provide a renewed focus to our work in this area."
The British Medical Association Scotland and Royal College of Nursing Scotland declined to comment on the research.