Staff at SE1's two NHS hospitals have been banned from smoking on the hospital campuses.
A ban on staff smoking on Guy's and St Thomas' two main hospital sites came into force on New Year's Day.
Guy's and St Thomas' NHS Foundation Trust says that it is now considering how it will extend the ban to include patients and visitors.
The trust's stop smoking service has helped more than 350 patients and staff to take their first steps towards quitting the habit since it was established in 2011.
Carina Oliveira, 27, who operates a machine that monitors patients' heartbeats at St Thomas', is one of them. She began smoking at age 17 to fit in with school friends and finally gave up her 10-cigarette-a-day habit in October.
Carina said: "My father died in August of lung cancer so I knew it was time to give up smoking myself.
"With the support of Nirmala Madadi, my stop smoking specialist, I have never looked back.
"The key is to remind yourself why you are doing it and to find the nicotine replacement therapy that works for you. Simple things like walking or swimming are relaxing and also take your mind off reaching for a cigarette."
Around 461,000 hospital admissions a year in England are due to smoking-related conditions such as heart disease.
Colin Bone, 54, and his partner Sandra O'Sullivan, 53, gave up smoking together in October.
Colin, from Bermondsey, had smoked for 43 years. He was spurred on to quit smoking after being diagnosed with breathing problems. His partner, Sandra, who smoked for 42 years, has also kicked a 25-cigarette-a-day habit.
Sandra, who comes to the stop smoking clinic for support every Friday with Colin, says: "I was shocked to find out that I had the lung capacity of a 90-year-old. That was it. I knew I had to do something.
"Following simple suggestions, like waiting four minutes to let the cravings subside, has made a real difference to my life.
"My daughter lives across the street in a block of flats without a lift. Now I can go up four flights of stairs and pop around to see my grandchildren without getting out of breath."
Stop smoking specialist Nirmala Madadi said: "Colin and Sandra are perfect examples that it is never too late to give up smoking.
"With the support of our stop smoking service, patients and staff can change their lives for good. There is no better time to stop smoking than today."
Last autumn the National Institute for Health and Care Excellence (NICE) published new guidance that all NHS hospitals and clinics should become completely smoke-free.
• Smoking inside the hospital buildings at Guy's and St Thomas' has been banned since 2005.