Chelsea started strongly and missed two gilt edged chances in the first ten minutes.
It was the young Dragons who took the lead through Fábio Vieira after eighteen minutes and it stayed that way until the interval. Eight minutes after the break Chelsea, twice previous winners of the competition, drew level when Castillo crossed for Redan to head home.
Two minutes later and Porto regained the lead through Diogo Queirós before Afonso Sousa made it safe fifteen from time when his shot found the back of the net via a post to make it 3-1.
FC Porto reached the final after beating Hoffenheim (Germany) 3-0 in the semi-final. Previously they had victories over Midtylland (Denmark), Tottenham Hotspur, Lokomotiv Moscow, Galatasaray (Turkey) and Schalke 04 (Germany).