They are different in size, skull shape, length of the muzzles, eyes, neck, and body. The Cavalier King Charles Spaniel is larger and heavier. Its skull is flat between the ears, whereas the King Charles spaniel has a well-doomed skull which is noticeably large in proportion to its body. The Cavalier has longer muzzles, whereas the King Charles has short and squarish muzzles. The Cavalier has big and round eyes, while King Charles's are noticeably large and are set wide apart. The neck of the Cavalier is more elongated and sophisticated. Finally, the body of the Cavalier is compact and equipped with a firm spring of rib, while the King Charles' is shorter and back level.