Obama was chatting privately with a U.N. official Monday and said he hoped the official had quit smoking. The exchange was caught on camera and aired on CNN.
After the official appeared to ask Obama about his own cigarette use, Obama said he hadn't had a cigarette in probably six years.
He added, with a broad grin, "That's because I'm scared of my wife."
Obama has acknowledged over the years struggling with tobacco use. Mrs. Obama said in 2011 that her husband had finally kicked the habit.
Monday's exchange came on the sidelines of the U.N. General Assembly in New York.