NEW YORK — David Letterman’s imminent retirement is bringing nostalgic viewers back to check out his final shows.

The Nielsen company said Letterman’s CBS “Late Show” had more viewers last week than the “Tonight” show for the first time since Jimmy Fallon took over last year, with the exception of when Fallon’s show was in repeats.

Letterman averaged 3.82 million viewers each night last week, compared to Fallon’s 3.09 million and 2.23 million for ABC’s Jimmy Kimmel, Nielsen said. Kimmel has announced that he wouldn’t air a new show on May 20, the night Letterman makes his final late-night broadcast before retirement.

So far this TV season, NBC’s “Tonight” show has averaged 3.96 million viewers, the “Late Show” has 2.83 million and “Jimmy Kimmel Live” has 2.72 million.

CBS said Thursday that actor Tom Hanks will be on Letterman’s show on May 18. Comic Bill Murray, a frequent Letterman foil, will be on Tuesday’s show.

CBS promised “surprises, memorable highlights and the show’s final Top Ten list” for Letterman’s final show, but announced no guests.