It seems doctors are practising what they preach.

A new study released by the University of Otago, Wellington, shows smoking has decreased in many occupations in the past 25 years.

It shows that under five percent of doctors in New Zealand smoke.

Professor Richard Edwards of University of Otago, Wellington, says the findings are encouraging.

"It just shows that you can get smoking down to very low levels which is exactly of course what we want to achieve in New Zealand which is pretty much trying to get rid of smoking by 2025."

People in "role model" occupations are being urged to consider the impact their smoking may have on the rest of the population.

Professor Edwards says while there aren't studies to prove the link, it is possible that people in influential occupations may have an impact on smoking levels.

"People like teachers or perhaps fashion models or sports people or people that are high-profile or who are influential because of their status or authority, they might influence people to think smoking is a normal thing to do."

The study was carried out using data from 1981 and 2006 censuses.

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