Openside flanker John Barclay, 20, was confirmed as the only uncapped player in the squad, which is captained by Jason White.
Hadden trimmed his 39-man training group to finalise the squad, with the players to miss out revealed as Simon Danielli, Nick De Luca, Alasdair Dickinson, Thom Evans, Alastair Kellock, Calum MacRae, Graeme Morrison, Gordon Ross and Alasdair Strokosch.
Hadden said: "I have selected a squad that has the ability to do something special at the World Cup and make our country proud. It is the most competitive squad we could muster.
"The decision to omit nine players from the squad was tough. I spoke with all but one of those players face to face yesterday (Monday) and thanked them for their huge contribution to the preparation for the 2007 Rugby World Cup."
Ross, who recently joined Saracens from Castres, emerged as the biggest casualty of Hadden's cull.
Chris Paterson's performance at stand-off in the 31-21 victory against Ireland on Saturday ensured that he and Dan Parks will contest that position, with 29-year-old Ross missing out.
The squad includes just 10 players with World Cup experience and consists of 13 backs and 17 forwards.
Hadden defended the decision to select a forward-heavy squad.
"It's not an uncommon split," he said.
"It reflects how tough it's going to be, especially for the forwards playing so many games in such a close period of time, and also reflects on that wee bit more flexibility within the backs.
"Overall this is a more mature group than we could have chosen two years ago.
"There's a fair amount of experience there and a good balance between the power that was demonstrated in our win against Ireland last weekend and a bit of footballing ability."
Glasgow Warriors rising star Barclay is relishing his opportunity, having watched the 2003 World Cup while still a school pupil.
He said: "I was injured at the time and I remember watching a Scotland game at my friend's house when I was meant to be watching the school team play."