David Cameron said you "couldn't put a value" on the free advertising for Northern Ireland as a result of the G8 summit.
The Prime Minister said his fellow G8 leaders had been impressed and added that he hoped it would help people realise how "magnificent" Northern Ireland is.
Mr Cameron used the summit's closing press conference to say he hoped the G8 had shown Northern Ireland was open for business.
Warm, sunny weather helped show off Lough Erne to the world and Mr Cameron even took a dip in the luxury golf resort's waters.
Mr Cameron acknowledged that many people associated Northern Ireland with "problems and divisions" but hoped the summit would help challenge that view.
The Prime Minister said: "I always wanted to bring the G8 to Northern Ireland and I'm really thrilled that we were able to do that and to find such a fantastic venue.
"It has, I hope, done a lot of good for Northern Ireland to demonstrate it's open for business, to demonstrate how beautiful it is and also how warmhearted and friendly the people are.
"I think all the fellow G8 leaders were really impressed by Northern Ireland. If you just read newspapers and had an interest over the last few years you couldn't help but associate Northern Ireland with problems and divisions and all the rest of it.
"It's only when you come and see it for yourself that you just see what a magnificent part of the United Kingdom this is.
"I think that the advertising, the infomercial, that County Fermanagh and Northern Ireland has had, you can't probably put a value on that. I'm proud that we have been able to deliver that free advertising for the businesses and people of Northern Ireland."