The UN has said the "emergency phase" is over in the areas affected by the Chernobyl nuclear plant disaster in Ukraine in 1986.
About five million people live in the contaminated areas
A resolution has been adopted by the General Assembly in New York.
It calls for continuing attention to "Chernobyl-related needs" but also urges a move to the "recovery phase".
A UN official said the body should now focus on rebuilding self-reliance of the affected population instead of treating them as victims.
The 1986 explosion spewed radioactive fallout over swathes of the then-USSR - including Ukraine, Russia and Belarus - and many other parts of Europe.
More than 330,000 people were forced to leave their homes after the world's worst nuclear accident.
Estimates of the number of deaths linked to the radiation leak vary widely, with the World Health Organization (WHO) putting the death toll at 9,000.
Experts are still studying the long-term effects on health, especially on children.
Tuesday's UN declaration proclaimed the next 10 years as a decade of "recovery and sustainable development" of the affected areas.
It said the focus should now be on helping the communities to reverse the domino effect of poverty, poor health and fear that had hampered growth in the region.
The General Assembly also requested the UN secretary general to provide a report on recovery efforts in 2010.
The declaration comes on the back of a report by the WHO which found "the health impact of the accident was much less severe than was initially feared", the BBC's Thomas Lane in New York says.
It also said the majority of the affected areas only suffered "low doses of radiation - doses that are close to naturally existing 'background levels'".
This paves the way for the UN to alter its aid structure to the region, namely parts of Belarus, Russia and Ukraine, our correspondent says.
Before the UN vote, Cihan Sultanoglu, a UN Development Programme (UNDP) official, said that "20 years of treating the residents of those regions as victims has created a culture of apathy".
Ms Sultanoglu said the UN's new role should be "to help rebuild a sense of self-reliance".
UNDP officials argue that "lifestyle issues" - like alcoholism and smoking - now pose a greater cancer threat than radiation for many residents in the affected areas.
The agency is already involved with various assistance projects, including giving advice and loans to small-scale farmers.
Ms Sultanoglu said the radiation resistance of several plants - including a rapeseed used in biofuels - held out hope for an agricultural revival.
Other UNDP officials suggested that eco-tourism might also help the region, our correspondent says.
But they conceded there would have to be plenty of attention to marketing, in order to overcome any "brand stigma" associated with Chernobyl.
Earlier this year, the UNDP made a first shot at this by appointing Russian tennis star Maria Sharapova as a "goodwill ambassador" for the cause.