Celtic were interested in the Pole, who hit all of Dortmund's goals in their 4-1 semi-final first-leg win over Real Madrid on Wednesday, but could not prevent his move to Germany in summer 2010 for a fee of around £4million.
Lennon, who took over as Celtic manager in March 2010, said: "I actually knew about Lewandowksi when he was at Lech Poznan. He might cost a few quid more now than he did then.
"We did look at him, two or three years ago, but we were never really in the hunt for him in terms of competition from other clubs. But we knew about him for a long time."