ABC was #1 last in the A18-49 demo thanks in part to the ABC News magazine “20/20.”

Last night’s show featured several reports on the Ft. Hood massacre as well as Diane Sawyer‘s interview with Rihanna, speaking for the first time about being attacked by her then-boyfriend, singer Chris Brown last February.

“20/20″ won its time period in Total Viewers (8.2M) and A18-49 (2.7 rating/9 share). The Elizabeth Vargas-hosted show was also Friday’s #1 TV show across each of the key demos: A18-34 (2.3/9), A18-49 (2.7/9) and A25-54 (3.1/9).

This was the show’s biggest audience in more than 7 months and its best A18-34 rating in almost 3 years — since Dec. 1, 2006.