Judges who didn't know which twin smoked said the smoker looked older 57 percent of the time, the New York Daily News reported.
That pattern held when both twins were smokers but one had smoked for many years longer than the other.
Dr. Elizabeth Tanzi said that smoking makes you look old.
She told Reuters Health that besides lung cancer, heart attacks and strokes, just one more good reason to stop smoking is that it's definitely making you look a lot older.
The findings are published in Plastic and Reconstructive Surgery.