There could be more than 2000 women across NSW who currently have breast cancer but don't realise it, BreastScreen NSW says.

Nearly half a million Australian women haven't had their recommended breast screening mammogram in the past two years, research shows.

That means there could be more than 2000 women in NSW who unknowingly have breast cancer, BreastScreen NSW says.

It has released new figures which show approximately 425,000 Australian women aged between 50 and 74 failed to put their hand up for the test in the past two years.

Modelling shows that if each of these women were to have their mammogram, at least 2000 of those living in NSW would be found to have breast cancer, it said.

BreastScreen NSW ambassador Jean Kittson said the results were disturbing considering more than 900 NSW women die from breast cancer each year.

"It's really distressing. It seems to me that over and over, women just don't know enough about their own health and how to look after themselves," she told AAP.

The Australian comedian said busy work and family schedules, as well as anxiety about the 20-minute tests, put many women off.

"What should be realised is that in the long run, it will help your family and friends if you prioritise yourself and look after your health," she said.

Ms Kittson said the screenings, which can find cancers as small as a grain of rice, were only mildly uncomfortable.

"Get a gang of friends together and make a day of it every two years," she said.

"(My friends and I) always make sure to have some cake and coffee afterwards."

BreastScreen NSW is launching a state-wide campaign on Wednesday to find the thousands of women who may have breast cancer.

With early detection, breast cancer survival rates can be as high as 98 per cent.

Breast cancer screening is free for women aged between 50 and 74, and no referral is needed from a GP.