Tuesday’s two-hour season premiere (9-11 p.m.) averaged 12.1 million viewers, up 6 percent from last season’s two-hour opener.

More importantly for ABC, the episode performed well among young viewers, finishing second to “American Idol” in adults 18-49.

It was the highest-rated “Lost” episode in adults 18-49 and 18-34 in nearly two years (since February ’08) — and was ABC’s best series numbers for a Tuesday (9-11 p.m.) in adults 18-34 since 2000.