Showing their world championship form to 13,909 wildly approving fans, the Boston Celtics jumped to an early lead and held off late Los Angeles Laker rallies last night to defeat L.A. 113-106, giving the Celtics a commanding 2-0 lead in the best of seven National Basketball Association playoff finals.

With the kind of point surge that has become their trademark the Celtics grabbed an 11 point lead in the third period after a see-saw first half. For the rest of the game Boston players took turns dashing Laker hopes of a comeback.

After six straight Los Angeles points narrowed the eastern division champs' lead to five points early in the final period, Bob Cousy and Sam Jones sparked a rally that made Boston fans comfortable again. The Lakers desperately fought back again, but Cousy sunk two quick field goals to widen the Celtics margin.

With two minutes remaining Jerry West and Dick Barnett combined to bring the challengers to within four points of Boston, but the Celtics' troubleshooter, Frank Ramsey, tossed in five of seven straight Celtics points to put the game finally out of reach of the Lakers.

The two teams will now travel to Los Angeles to play the next two games.