We bought the medium sized bed for our cocker spaniel and it's the perfect size - big enough for him to stretch out on, and also, with the raised sides, cosy enough for him to snuggle into. At first he wasn't sure about it because it's much thicker than his old bed, and he didn't seem sure if he was supposed to actually lie on it! But now, it's the only place he sleeps, and he hardly moves, so it must be really comfy.