I got my dog several years ago, and people kept telling me that my Cavalier King Charles Spaniel was really a King Charles Spaniel (without the Cavalier part). I did not know the difference between these supposedly two different breeds. Since then I have learned the difference isn't very much except in size and to the breeders.
In the late 1600s the King Charles Spaniels were interbred with Pugs, which resulted in a smaller dog with flatter noses, upturned faces, rounded heads and protruding eyes. It was developed in the
Cavalier King Charles Spaniel
If you are looking for one of the most charming companions in the canine community, consider the Cavalier King Charles Spaniel. Cavaliers are the largest breed in the Toy Dog category and make wonderful pets for people with many different lifestyles.
Cavalier Spaniels are indoor dogs that were traditionally bred as lap dogs. They become quite attached to their "people companions" and do not tolerate being left alone for extended periods of time well. If your pet will be alone often, particularly as a puppy, consider choosing a breed that has less separation anxiety than a Cavalier.