But doctors in London say Mario Scaramella shows no symptoms of radiation poisoning.
Keith Patterson is a consultant for University College Hospital in London.
"Tests have detected polonium-210 in Mr. Scaramella's body, but at a considerably lower level than Mr. Litvinenko," he said. "He is currently well and shows no symptoms of radiation poisoning. He is receiving further tests over the weekend."
Scaramella, an Italian academic and self-described security expert, met with Litvinenko in a London sushi bar on November 1, the day Litvinenko became ill.
Litvinenko's wife has also tested positive for slight contamination by polonium-210, but so far has shown no serious health effects.
Meanwhile, four Greeks who stayed at the same hotel as Litvinenko are undergoing preliminary hospital tests for radiation toxicity.
(compiled from agency reports)