The Prince of Wales has admitted smoking behind a chicken coop when he was a boy.
Speaking to a group of respiratory nurses, Charles said he quit smoking at the age of 11.
The 64-year-old told the group about the rebellious act at a reception at Clarence House.
Nurse and secondary school teacher Paul Watson, 39, from Peterborough said: "There was a few of us that are respiratory nurses and he asked whether we deal with a lot of smokers.
"He said 'I gave up at 11 when I had a few cigarettes behind a chicken coop'.
"I believe it was tongue in cheek."
The remarks were made at a reception Charles hosted to pay tribute to the nominees of the Nursing Times annual awards.
Earlier today ,Charles hailed the dedication and hard work of the nation's nurses, saying they give "exceptional care" to patients across the country.
Writing in the Nursing Times ahead of the magazine's awards ceremony tonight, he said he believed nurses' care and kindness was "vital" and stressed the importance of a holistic approach to those who are sick.
Charles, who is patron of more than 30 healthcare organisations, said his visits to hospitals over the past 40 years had shown him just how pivotal a role nurses play.
He wrote: "In all these instances, together with many others, it was abundantly clear to me just how important the emotional connection between patients and skilled, hardworking nurses actually was.
"In general, quite apart from the medical expertise that nursing staff provide on a daily and nightly basis, the reassurance and simple human kindness that they can also dispense is, I believe, vital and must surely impact positively on the recovery of individuals.
"Human kindness, reassurance and sympathy are age-old qualities, yet they are as important today as they have ever been.
"The Nursing Times Awards recognise this, as well as the importance of a holistic approach - treating the whole person, rather than just the symptoms of disease.
"When this approach is combined with the best of conventional medicine, and adopted by the whole healthcare team, with scrupulous attention to every aspect of the patient's personal, medical and nursing needs, great progress can be made."
At the reception, Charles met many of those nominated including nurse Victoria Harmer who is in the running for the Cancer Nurse of the Year award.
She said she also helped to alter the scripts when the actress who plays the role, Sally Dynevor, was diagnosed with the disease in real life.
The 41-year-old, from central London, said: "I did help to write the scripts for The Archers for BBC Radio 4 when Ruth had breast cancer and also I helped a couple of years ago when Sally Webster was diagnosed with breast cancer on Coronation Street.
"It's really important not to scaremonger, to get the salient points across and to get correct information out there.
"I think the average viewers of Coronation Street are post-menopausal women who, of course, are most at risk of breast cancer."
Charles said those nominated for the awards, in 19 categories, are making a "tangible difference" to people's lives, singling out nominees including Melissa Rochon, from the Royal Brompton Hospital, who carried out a study into why some patients were more susceptible to infection than others, and Nina Turner, a nurse at Maidstone Prison, who is trying to improve the care of prisoners with chronic lung disease.
He added: "The nominees I have mentioned are just a few of the many thousands of nurses who understand the value of the 'human touch' and who are committed to working day in, day out, in hospitals and in the community, to give patients, carers and families exceptional care.
"It strikes me that we must support them in their work and recognise their contribution however we can. It is impossible to express the value of the care they give, often when people are at their most vulnerable, and I can only congratulate them on all their achievements."
NHS England's chief nursing officer, Jane Cummings, and Dr Peter Carter, chief executive and general secretary of the Royal College of Nursing, welcomed the Prince's support of nurses.
Ms Cummings said: "I have just been talking to the nurses that have been shortlisted and they are just overwhelmed that someone is actually recognising the good work that they are doing.
"It's really nice for staff that do feel a bit battered at the moment by some of the relentless bad press that they get."
Dr Carter said: "It reinforces that the Royal Family, like the vast majority of the British public, still hold nurses in huge respect.
"Whilst there has been some criticism, we must remember that the vast majority of patients consistently express high degrees of satisfaction with their care.
"It's not to deny that there are issues and challenges but most nurses are nothing other than decent, reliable, upstanding citizens."
Head and neck cancer nurse specialist Julie Hoole, who works for Mid Yorkshire NHS Hospitals Trust, said: "With nurses struggling to prove their value and worth, this highlights all of the hard work that is being done around the country."
:: The Nursing Times Awards are taking place at the Grosvenor House Hotel in London's Park Lane this evening.