The president is a well-known basketball fan, while the prime minister was attending his first basketball game -- one in which Western Kentucky beat Mississippi Valley State 59-58 in a South Region play-in game to reach the second round for a game Friday against Kentucky, the top seed in the South Region.
Obama and Cameron sat in a section behind one of the baskets at University of Dayton Arena, accompanied by Ohio Gov. John Kasich, White House Chief of Staff Jack Lew and Cameron Chief of Staff Ed Llewellyn.
Obama and Cameron each had a hot dog and the president chatted with students sitting nearby.
At halftime, Obama and Cameron were interviewed on CBS.
Cameron said he was enjoying the experience, even though it was "hard to follow sometimes exactly who's done what wrong." He said Obama offered to "help me fill out my bracket" and Obama said Cameron offered to help him understand cricket because "I don't understand what's going on with that cricket thing."
Obama said he probably won't be able to watch much of the tournament except for the Final Four, "and even that I may end up seeing in snippets."
Asked whether he thinks Obama will be re-elected in November, Kasich -- a Republican former member of Congress -- demurred.
"Oh, it's not a night to talk about all the election stuff," he said. "It's a time to have some comfortable time together."