The mortality rate among males of a young working age is 44% higher than the average on the continent, and 48% higher for females in the group, according to a study by the Glasgow Centre for Population Health (GCPH).
It says alcohol abuse, drugs and suicides have largely contributed.
Mortality rates among adults aged between 15 and 44 have got progressively worse in the past 55 years.
The report said: "As a result of these trends compared to other European countries, Scotland's relative ranking for younger working age mortality has become progressively worse over the last 55 years.
"In the late 1950s Scottish male mortality in the age group was ranked as ninth highest, but by 2004 Scotland was ranked first. The pattern for women is similar."
Male adults were more likely to die young in Scotland when compared with those in other parts of the UK, with the gap continuing to widen.
In 2009 the death rate for young adults north of the Border was 54% higher than in England – more than double the rate recorded in 1950.
The report added: "The death rate for Scots in this age group is now 54% higher when compared to England, with this health gap widening over 60 years."
Author Bruce Whyte, public health programme manager at GCPH, said: "There has been no improvement in Scotland's mortality rates in the younger working age group at a time when other countries have improved.
"We know there are issues with alcohol, with alcoholic cirrhosis of the liver, accidental poisonings and suicides.
"There has also been a small contribution from things such as breast cancer and heart disease but we know the contribution of these chronic diseases is less."
The study looked at mortality rates in Scotland and 19 other European countries between 1960 and 2010.
It found improvements in death rates for conditions such as heart disease, stroke, and several forms of cancer.
However, the report also highlighted concerns about mortality of elderly women and the number of females dying from lung cancer. It also recorded that Scotland had the worst mortality rates in western Europe among working age men and women aged between 15 and 74 for more than three decades.
It said: "Mortality in the working-age population remains comparatively high and mortality for circulatory diseases and many cancer-related diseases is higher than in most other western European countries."
Public health minister Michael Matheson said overall health was getting better in Scotland.
He added: "We are working to address early mortality in younger working age people by taking significant action to cut alcohol consumption, reduce smoking rates and drug addiction, to encourage active living, healthy eating and wellbeing."