The 33-year-old is among the favorites to add a second downhill gold to her 2010 title from Vancouver, but she cried as the emotion of losing her grandfather, Don Kildow, at the age of 88 in November came flooding back in her first Winter Olympics news conference Friday.
CNN's Coy Wire asked the American how memories of her grandfather resonated with her now she was in South Korea preparing for the Games.
"Ah, it's really hard," replied Vonn, the most successful female ski racer of all time.
"I wish you wouldn't have said that. It's really hard for me not to cry."
She paused before adding: "Yeah, I just want so badly to do well for him and... I miss him so much."
Vonn teared up as she continued: "He's been such a big part of my life.
"And I really hoped he'd be alive to see me but I know he's watching and I know that he's going to help me. And... I'm going to win for him."
Vonn missed the Sochi Olympics because of a knee injury, and struggled for much of last season after breaking her arm and suffering nerve damage in her hand.
But she has won four World Cup races this season, including back-to-back downhills coming into the Games, to close to within five victories of the all-time record held by Sweden's Ingemar Stenmark.
She also won super-G bronze at Vancouver 2010.
Vonn says without her grandfather's influence she may never have taken up the sport.
"If it wasn't for my grandfather I wouldn't be racing," Vonn told CNN's Alpine Edge
in St Moritz, Switzerland in December.
"My grandfather taught my father how to ski. It's because of him that it is in our family. It was a huge loss to me and my family. I think about him all the time, especially when I'm racing. And I feel closer to him when I'm skiing."