A study of the health behaviour of over 13,700 Irish school children has found that about half of pupils aged 15 to 17 years drink alcohol.
A third of this age group reported being 'really drunk' in the previous month.
On drug use, 12% of pupils reported using cannabis in the last year, some as young as 10 years of age.
The study, which involved 215 schools and pupils aged 9 to 18, was conducted last year by researchers at the Health Promotion Research Centre at NUI Galway.
It was undertaken as part of a collaboration with a major World Health Organisation project.
The vast majority of those surveyed said they were happy with their lives and were in good health.
The number of children smoking continues to decline, with only 15% saying they are current smokers.
Compared with a similar study in 2002, the percentage of children eating sweets and soft drinks has fallen and vegetable consumption is up.
But 14% of children report that they never have breakfast during weekdays and 12% are seeking to lose weight.
