His mother, Tracy O'Connor, 37, held the celebration, at Formby Guild Hall, to honour her son's wishes.
She said: "Since we lost Lee, it has been hard every day. He is on my mind constantly.
"This was something I had to do. He was looking forward to his 18th and he wanted a party.
"Being surrounded by his family and friends made the day a lot easier."
Carer Mrs O'Connor described her son as an "outgoing and loyal" teenager who loved his job.
She said: "He had lots of friends. Even his boss was his best mate.
"He was going up in the company very quickly and he was made up to have passed his test. It meant he would get a pay rise, and he was one of the youngest boys to do it."
Lee, a former pupil of Formby High, enjoyed playing pool and watching his beloved Liverpool Football Club.
Mrs O'Connor added: "I am still very close to his mates. They come round to see me and have helped me a lot since the accident."