A rethink of headteachers' role is needed to stem the fall in applications for their posts, said Sean Cottrell, director of the Irish Primary Principals' Network.
Teachers are put off from applying by excessive workload, the burden of responsibility, insufficient pay and lack of training, according to a survey carried out by the IPPN.
Another factor was whether staff felt they would have the power to develop the school.
The survey drew on responses from 1,250 Irish teachers and 250 other teachers internationally, most of them from Canada, Australia, South Africa and the United States.
In Ireland, the number of applications for each primary headship had fallen from 3.9 in 2000 to 2.9 in 2004; while the numbers applying for secondary headships had fallen more steeply from 2.5 in 2000 to 1 in 2004.
Mr Cottrell said more than half the teachers in the survey said they definitely or probably would not apply for a headteacher post.
"Lifestyle was a major reason why females did not apply," he said.
Pat Newman, president of the New Zealand Principals' Federation, said: "We have become poor role models by showing staff this is a person overstressed and overworked, so teachers are saying, 'We don't want your job'."
Mr Cottrell said job-sharing could draw more women applicants, and giving heads study leave and travel opportunities could increase the job's attraction.