The Scandinavian Defence is definitely one of the neglected sidelines of the contemporary opening theory.
Only just a few grandmasters dare to include it in their opening repertoires at high level once in a while.
The Caro-Kann Defence leads to positions that are sometimes similar to the Scandinavian Defence if you have in mind the pawn structure and the standard opening strategy.
On the other hand, contrary to the not so solid Scandinavian Defence, it enjoys the reputation as the opening of the chess-academics.
Capablanca, Botvinnik, Petrosian and Karpov - this list of great chess-champions that have been life-long devotees of the Caro-Kann Defence can be easily extended.