Volunteer roles are often the first to suffer in a time squeeze, according to Hunter Volunteer Centre manager Tony Ross. But that doesn't mean there are fewer volunteers.

In fact, about 230,000 people volunteer for more than 30,000 organisations across the Hunter.

"There are more people volunteering than ever before but they're volunteering for less time," Mr Ross said.

He believes work, education and social pressures are the reasons.

This week, from May 11 to 17, is National Volunteer Week.

Established in 1989, the annual celebration of volunteers is the largest in Australia.

It aims to recognise those who donate their time to their community, whether it be 20 minutes or seven days a week.

Mr Ross said this was an important aspect of National Volunteer Week.

"If someone says they've only got 20 minutes to give, it's likely that's all they've got," he said.

"But it's the offer that counts; that's the bit that should be celebrated."

This year the campaign's theme is Give Happy, Live Happy, which highlights the physical, mental and emotional benefits of volunteering.

According to Volunteering Australia's website, these include a greater sense of self-worth; improved mental health and increased longevity.

■ Go to volunteeringaustralia.org for more information on National Volunteer Week.