Some websites and chatrooms pose a "growing danger" in terms of encouraging suicide and some have led to the deaths of young people, according to the Samaritans.
At an event to publicise new guidelines on the reporting of suicide, Mike Cobb, a spokesman for the charity, also told the media that reporting certain details of suicides could lead to "copycat" attempts.
Media Guidelines for the Portrayal of Suicide
"This year and last year the print and TV media have supported Samaritans in what can only be called a battle against the dangers of suicide websites and chatrooms and how they have led to the deaths of too many youngsters, a problem which is particularly bad in Japan," he said.
"These are referred to in the media guidelines as a growing danger. But in some of their enthusiasm to condemn these websites for causing the UK's first suicide pact some months ago, some of the print media then wrote far too much detail on the method used by the couple concerned, and that method is now becoming far more common," Mr Cobb said.
The media guidelines note a "growing culture of people using chat rooms on the net to meet, discuss and plan their suicides.
"There are also reports of people in chat rooms urging each other on to end their lives," the booklet states.
"The Internet is much more interactive than many other media, and this makes it potentially more influential in relation to suicide than other media."
The Samaritans received 11,000 text messages within just three weeks of setting up a support service for people at risk of self-harm or suicide last April.
The text service saw an four-fold increase in the number of texts following a recent episode of the TV soap Hollyoaks, where a character was considering suicide.
The new media guidelines were published by the HSE's National Office of Suicide Prevention, in conjunction with the Irish Association of Suicidology.
They offer advice for all media - including newspapers, television and radio as well as online media and producers of theatre and television drama.
Journalists are urged not to use certain phrases in reporting suicide and not to romanticise or glorify the act.
Suicide is the biggest cause of death among men and women under the age of 35 on the island of Ireland. Some 431 people died by suicide in 2005.
Minister of State at the Department of Health Tim O'Malley said suicide is an issue affecting everyone in Irish society, and that it was an issue that had affected him personally.
He said there was now "huge awareness" of the issue of proper mental health and positive mental health. "It does not just impact on the medical profession or educationalists," he said.
Geoff Day, National Office for Suicide Prevention
Unfortunately, Ireland as a society had not traditionally dealt well with suicide and people were not well trained to deal with it until recently, he said.
The huge problems in Irish society such as sexual abuse "were not even spoken about 10 years ago".
Geoff Day, head of the HSE's National Office for Suicide Prevention, said: "While it is appreciated that suicide is a legitimate subject for media coverage and reportage, certain types of portrayals and reporting are potentially harmful, and can act as a catalyst to influence the behaviour of those who are already vulnerable.
"Nevertheless, the media has an extremely important role to play in educating the public about suicide and the wider issues involved that may lead people to feel suicidal."
The Samaritans may be contacted 24-hours a day on 1850 609090 or by text at 0872 609090.