THERE was some better ratings news for Conan O’Brien and his “Tonight Show” last week.

While O’Brien once again was beaten by David Letterman’s “Late Show” in total viewers — a common occurrence this summer — O’Brien handily defeated Letterman in the “young viewer” demos so coveted by NBC suits.

“Tonight,” in fact, beat “Late Show” by 63 percent in adults 18-49 — its biggest margin over Letterman in that demo since late June — and by a whopping 144 percent in adults 18-34.

And, if we’re talking about “young viewers,” the median age of O’Brien’s audience was 46 — compared to 56 years old for Letterman viewers, according to Nielsen.

Still, Letterman averaged 3.3 million viewers to O’Brien’s 2.8 million viewers — but it was ABC warhorse “Nightline” that claimed the total viewership crown with 3.5 million viewers.

(“Nightline” airs from 11:35 p.m.-12:05 a.m.; both “Tonight” and “Late Show” air from 11:35 p.m.-12:35 a.m.)