The Celtics have won the Championship 17 times...
Twelve times. The Celtics have won nine of the championship meetings.
None because the Lakers Reign Supreme
Celtics won 17 NBA Championship.
Once. The Celtics defeated the Los Angeles Lakers in six games to win the 2007-2008 NBA title.
Twice. In 2008, they defeated the Los Angeles Lakers in six games. In 2010, the Lakers defeated the Celtics in seven.