Although the Flyers and Bruins have existed in the same conference (Wales/Eastern) since the 1981-82 season, they have not met in the postseason since 1978.
In fact, the teams met four times in a five-year span in the playoffs during the 1970s, with each club winning two series.
Philly won the 1974 Stanley Cup Finals over Boston in a tremendous upset, 4 games to 2, then took the 1976 Semifinals 4 games to 1 -- with Reggie Leach memorably shaking off a hangover to score five times in the clinching 6-3 Game 5 victory at the Spectrum.
However, Boston got its revenge in the next two series, advancing to the Cup Finals in both 1977 and 1978 by trampling the Orange and Black. The former series was a four-game sweep, while in the latter the B's let the Flyers take one game. Both times the Bruins lost to Montreal in the Finals.