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It was screened as a special edition to mark the first anniversary of her death on 26 April.
The police officer leading the inquiry, Detective Chief Inspector Hamish Campbell, said people were ringing in with "very precise" information.
"A lot of names, two names have been mentioned twice and that is the sort of information we need," he said.
He said many of the 400 calls were from "well meaning members of the public" but did not add anything to the investigation.
DCI Campbell said about 200 names were put forward and of these around 20 were described as "relevant and interesting" .
Killer may have watched
Two of the names were put forward by more than one person.
DCI Campbell believed the killer would have been watching the programme and made a personal appeal for him to give himself up.
He also revealed that a woman with the same surname was phoned by a man asking for details about the TV presenter.
He said the call lasted for 10 minutes, and the man pushed her for as much information as he could.
"It was a very polite, respectful call. She described him as a white person with no foreign accent," he said.
'Acting suspiciously'
Mr Campbell said the man had specific questions about Jill Dando. The call was made in the months before Jill Dando was killed.
Detectives involved in the hunt also say they have uncovered new witnesses who saw a man acting suspiciously near Miss Dando's home beforehand.
Several people have come forward who, in the days leading up to the shooting, saw a tall, agitated-looking man near the house in Fulham, south west London.
Miss Dando, 37, was shot at close range as she returned home last April. The gunman fled.
Several witnesses said the suspicious man was wearing a suit too big for him and carrying a mobile phone.
Obsessive fan theory
Detectives are understood to believe that Miss Dando's killer may have been an obsessive fan who secretly watched her home for several weeks before shooting her.
The suspect is a smartly-dressed man in his thirties or forties with dark hair, a Barbour-style jacket over a blue suit, and has been described as looking "like an estate agent".
At least two neighbours saw him within about 90 minutes of the murder, according to reports.
Detectives suspect that could have been part of a plan to make an attempt to introduce himself to Miss Dando, who was selling her house at the time.
It is reported that in the run-up to Miss Dando's death, he may have communicated with her, perhaps by letter, and was rebuffed.
Another theory, apparently favoured by Miss Dando's fiance Dr Alan Farthing, was that she was executed by a stalker who could not cope with the idea that she was soon to marry.
Officers have not ruled out the theory that she was the victim of a contract killer but no one has come forward with credible information, despite a £250,000 reward.