The 31-year old South Korean midfielder has signed a two-year deal with the R’s after seven years at Old Trafford and Hughes feels it is a massive signing for the West London club.
"This is a real coup for QPR," he told the club's official websit. "We are delighted Ji is going to join us because his record speaks for itself.
"He has been a big player for Manchester United and played a big part in their success in recent years.
"He is hugely respected there because of what he has achieved, his application to his work and the impact he has on games.
"He was always picked for the big matches because they could rely on him, and we are going to reap all those qualities.
"We were able to show him where the club is heading and he embraced it. Ji gets what we are trying to do. This is a huge signing for this football club."