According to the group's report released Tuesday, nearly 400,000 volunteers scoured about 17,000 miles of coastline, river bottoms and ocean floors during its 23rd International Coastal Cleanup in September.
Cigarette butts topped the list of trash collected with more than 3.2 million. That's followed by about 1.4 million plastic bags. Volunteers also collected 26,585 tires, enough for 6,646 cars - and a spare.
Of the 104 participating countries, about half the volunteers were from the U.S. The Philippines, Canada and Japan had the largest international turnout.
The next cleanup is Sept. 19.
Top 10 debris items found worldwide during the Ocean Conservancy's International Coastal Cleanup in September 2008:
1) Cigarettes and filters, 3,216,991
2) Plastic bags, 1,377,141
3) Food wrappers and containers, 942,620
4) Caps and lids, 937,804
5) Plastic bottles, 714,892
6) Paper bags, 530,607
7) Straws and stirrers, 509,593
8) Cups, plates, forks, knives and spoons, 441,053
9) Glass bottles, 434,990
10) Drink cans, 401,412