Fox captured Thursday night among young adults thanks to a special results-show edition of “American Idol,” while CBS prevailed in adults 25-54 behind dramas “CSI” and “Without a Trace.”

According to preliminary nationals from Nielsen, “American Idol” (10.6 rating/27 share in adults 18-49, 26.3 million viewers overall) was Thursday’s top show in key demos, on par with its week-ago perf on the night; “Idol” reverts to a twice-a-week (Tuesday/Wednesday) format next week. The music competition led into “The OC” (3.5/9 in 18-49, 7.5 million viewers overall), which returned from a hiatus with its season-best scores — although it merely held a third of its huge lead-in.

At CBS, “Survivor: Exile Island” (5.3/14 in 18-49, 15.3 million viewers overall) placed second to “Idol” but was again lower than usual, as was slot-leading “CSI” at 9 (8.8/22 in 18-49, 27.2 million viewers overall), which remained Thursday’s most-watched program overall. “Without a Trace” closed out the night with solid results for the Eye (first-place 6.6/18 in 18-49, 20.3 million viewers overall).

ABC got decent numbers, at least after “Idol” ended, for theatrical “Bringing Down the House” (2.3/6 in 18-49, 7.3 million viewers overall), and “Primetime” was on par at 10 (2.5/7 in 18-49, 7 million viewers overall).

NBC’s all-repeat lineup was led by “My Name is Earl” at 9 (4.1/10 in 18-49, 8.8 million viewers overall).

Preliminary 18-49 averages for the night: Fox, 7.1/18; CBS, 6.9/18; NBC, 3.0/8; ABC, 2.4/6; WB, 1.4/4; UPN, 0.8/2.

In total viewers: CBS, 21.0 million; Fox, 16.9 million; ABC, 7.2 million; NBC, 6.9 million; WB, 3.4 million; UPN, 2.1 million.