Jay Leno returned to his late night spot, but the ratings haven’t come back.

Deadline Hollywood reports that “The Tonight Show” posted its lowest Q2 ratings during Q2 2010 — the first full quarter since Leno took the show back from Conan O’Brien — since rival David Letterman’s “The Late Show” debuted on CBS in 1993.

Leno’s “Tonight Show” (4.0 million total viewers, 1.1/4 A18-49) beat Letterman’s “Late Show” (3.3 million total viewers, 0.9/4 A18-49), but was still down 20% in viewers and 31% in A18-49 from last year’s Q2 (though those ratings were high due to Leno’s farewell and Conan’s debut).