Prime Minister John Key says 10 years on from September 11 and the international military response to it, he "would like to think" the world is a safer place.
Commemorative events are being held in the United States and around the world to remember almost 3000 people from more than 90 countries who were killed in the attacks.
Key said the world had changed as a result of 9/11.
"We live in a very different environment," he told TVNZ's Breakfast programme.
"Even when it comes to something like preparing for the Rugby World Cup, we have to be very vigilant there could be a risk of global terrorism, even though we have no known or prescribed threat, we still have to take that seriously.
"Probably in 1987 when we hosted the Cup it was very different."
New Zealand still faced a low risk of terror attack despite its involvement with the NATO-led force in Afghanistan, Key said.
"Every one around the world faces a risk but it's fair to say we are also a much lower risk environment than a lot of other parts of the world. But it's always possible."
Afghanistan was "arguably safer" because of the response to 9/11, he said.
However, there had been a big cost to pay because many people had lost their lives.
"If you think about Afghanistan, that was a place where Al Qaeda used that environment to plan and plot global terrorism.
"I think that's generally not happening in Afghanistan. It doesn't mean activities haven't moved to other parts of the world and we're all concerned about other environments."
Who won the leaders' election debate?Related story: Debate turns slug-fest