Dana Reeve, the widow of Christopher Reeve who nursed the paralysed Superman for nine years, stunned Americans on Tuesday by announcing she had been diagnosed with lung cancer.

Reeve, 44, who earned respect and affection for devoting herself to her husband after a riding accident left him paralysed from the neck down, said she was undergoing treatment and was optimistic about her prognosis.

But the news that the deadly disease had afflicted a relatively young woman who is also a non-smoker came as a shock after the death on Sunday of veteran TV news anchor Peter Jennings, who had been a heavy smoker.

"Now, more than ever, I feel Chris with me as I face this challenge," Reeves said in a statement. "As always, I look to him as the ultimate example of defying the odds with strength, courage and hope in the face of life's adversities."

"My family and I deeply appreciate the care and concern of our friends and supporters and trust that everyone understands our need and desire for privacy during this time. I hope before too long to be sharing news of my good health and recovery."

Reeve, a singer and actress who has a 13-year-old son with Christopher Reeve, put her Broadway and TV career on hold to nurse her husband after his 1995 accident until his death in October 2004.

She also worked with Reeve to rally support for research on the treatment of spinal cord injuries and is currently chairwoman of the Christopher Reeve Foundation. A Foundation spokeswoman said Dana Reeve was not a smoker.

Campaigners for lung cancer research said they hoped Reeve's announcement would raise awareness and funding into anecdotal reports from doctors that it is affecting increasing numbers of non-smoking, younger women.

Ten to 15 per cent of lung cancer victims are non-smokers and women in that group are twice as likely to get the disease than men who don't smoke. Radon gas, passive smoking, genetics and pollution are some of the causes among non-smokers.

"I know of a woman who got it at 32, one at 33, at 38 years old. They are all never-smokers, runners, healthy as horse kind of people. There are a lot of factors that we simply don't know yet," said Regina Vidaver, executive director of the non-profit group Women Against Lung Cancer.

Vidaver said lung cancer receives 10 times less funding per death than breast cancer in the United States yet it kills almost twice as many women as breast cancer.

"Thank God for people like Dana Reeves and Peter Jennings for coming out and saying 'I have this disease.' A lot of people will not come out of the woodwork because they feel like it's a self-inflicted disease and there is a stigma," Vidaver said.

The Christopher Reeve Foundation said its prayers were with Dana Reeve, who went public ahead of an imminent tabloid news story about her health.

"We are certain that Dana will tackle this challenge with the grace, courage and determination that have become her hallmark," Foundation President Kathy Lewis said in a statement.