"I'm not even sure I wanted it, to tell you the truth," Scalia told reporters at a media briefing before a gala dinner at the Waldorf Astoria Hotel in Manhattan.
Bush, who had in the past mentioned Scalia as one role model for an ideal chief justice, passed on Scalia and nominated John Roberts (search) after Rehnquist's death.
Scalia said the time he would have had to devote to administering the court as chief justice would have taken away from his thinking and writing. However, he said, "The honor would have been wonderful."
Asked if he knew why he wasn't nominated, Scalia said the reason "is locked in the heart of the president."
Scalia was the only justice who did not attend a Sept. 29 White House swearing-in ceremony for Roberts. Scalia said Saturday that he had a commitment that could not be broken.
According the Federalist Society Web site, he was leading a two-day seminar on the separation of powers in Avon, Colo.
Questioned about Harriet Miers, Bush's nominee to replace retiring Justice Sandra Day O'Connor, Scalia said he had never met her.
"Never having met her, I have no impression of her," he said.
Scalia, who is of Italian-American heritage, was in New York to serve as the grand marshal of Manhattan's Columbus Day Parade on Monday.
Scalia was scheduled to participate in a wreath-laying ceremony Sunday to commemorate the explorations of Christopher Columbus. He was among a handful of honored guests of the Columbus Citizens Foundation, an Italian-American group organizing the parade.