The CDW can cover up to 100% of any collision damage - the actual percentage will differ between companies and from country to country. A nasty poisoned pill has crept into a lot of car hire contracts lately: you make a contract to hire a car, take out what you think is full insurance (CDW) but when signing out the car you are told that covers collision but not other damage (from whatever cause) and that your liability is many hundreds of euros/pounds. In fact this detail is buried in the fine print when you hire (e.g. online). You are then invited to take out further insurance to cover this "other" damage or most of it - for X a day. I have experienced this in Germany and Ireland recently and you are faced with a choice of taking the risk or else substantially increasing your hire cost for peace of mind.