Lukaku chose United over Chelsea to be reunited with Mourinho, with the Special One revealing why he decided the former Everton striker was the right man to replace Zlatan Ibrahimovic as his main striker.
Mourinho sold Lukaku to Everton in his second spell at Chelsea, but denied there was a falling-out between them over the issue, insisting they remained close even though they were at different clubs.
“It’s quite a great experience the fact we worked together already for a few months,” said Mourinho.
“During the time when I was at Chelsea and then United, and he was at Everton, our relationship was always very close, despite not working together.
“He’s intelligent, he’s polite, we kept the contact, the feeling, and now we are back together in different moments and I have no doubts it is going to work.”
Asked to compare Lukaku to his former Chelsea striker Didier Drogba, Mourinho said: “I don’t compare, I don’t compare at all. One has his history and one is still in the beginning of his history.
“What he brings is hopefully goals. He’s the kind of player that everybody knows he’s a striker, so we’re not speaking about a multi functional player or one where there are doubts about his position on the pitch.
“He’s a striker and normally strikers score goals and the reason why he was so important and difficult to get is what he did in the Premier League.
“He has played in the Premier League for the last four or five seasons, so now he comes to a club with a different responsibility than Everton or West Brom.”