Sam, 11, who's already won three top gongs this year for playing Chesney, said: "Thank you to everyone who voted for me... I've had a mint year."
His co-star Suranne Jones, who plays Karen, took most popular actress.
Ant and Dec won two awards - for most popular entertainment presenter and most popular entertainment programme.
It was the second year in a row that their Saturday Night Takeway has triumphed in its category.
Jonny Wilkinson's last-minute drop-goal in the rugby World Cup final was named best sporting moment.
The awards, screened live on telly, are the only TV prizes to be voted for entirely by the public.
And viewers were voting for best serial drama right until the end of the show - when Coronation Street scooped the honour!
Hear story 
National TV Awards 2004 - winners
Who would you like to see on a TV show?
Which soap is best, Corrie or 'Enders?
