Three out of four adults surveyed said they had family, friends or acquaintances with some form of mental illness.
Nearly one in 10 of the respondents suffered from a mental illness, according to the survey commissioned by Mental Health Ireland to gauge attitudes toward mental illness in Ireland.
The State-wide telephone survey was conducted on 1,000 adults who reflected the demographic profile of the Republic as a whole.
Of the 73 per cent of respondents who knew someone with a mental illness, 39 per cent knew someone in their immediate family, 25 per cent knew a friend or acquaintance and 10 per cent knew a colleague or someone else who suffered from a mental illness.
Depression was the most common illness suffered by respondents and their family and friends. Schizophrenia, anxiety disorders and eating disorders were also cited.
The high incidence of personal experience with mental illness was attributed to the positive attitudes toward mental illness among those surveyed.
For instance, 96 per cent of respondents agreed that a far more tolerant attitude was needed in society toward people with mental illness, while 98 per cent agreed society has a responsibility to provide the best possible care for mental illnesses.
Mr Brian Howard, chief executive of Mental Health Ireland, said the majority of those surveyed had a very informed perception of mental illnesses. The results showed support for increased mental health services. Almost seven in 10 adults felt there were insufficient services and 95 per cent agreed that increased spending on mental healthcare would not be a waste of money.
"It's a very clear signal here to the Minister of Health and Children that there is a very clear mandate, and it would be a very popular measure to actually increase investment in the delivery of mental health services," Mr Howard said.
The survey showed support for integrating mental illness sufferers into the community, with 89 per cent agreeing that the best therapy was to be a part of a normal community.
Nearly 81 per cent felt residents had nothing to fear from people coming into their community for mental health services.
However, 6 per cent said they would not want to live next door to someone who has been mentally ill and 18 per cent felt that locating mental health facilities in residential areas downgraded the neighbourhood.
The negative views toward mental illness made up a sizable minority in the survey. Almost 30 per cent felt there is something about people with mental illness that makes it easy to tell them from "normal people".