Currency in Croatia

Always use the local currency (wherever you are) - in this case, Kuna.

Definitely the Kuna. We saw prices quoted in both but our money went further when we did our transactions in Kuna.

I believe that they print prices in Euro either for the convenience of European tourists and/or because the Kuna value changes too frequently. So, as in Turkey, if a hotel price is published in Euros, for instance, they'll use that day's exchange rate (posted at the reception desk) to calculate the price you actually pay in Kuna.

Definitely Kuna. Many places quote amounts in Euro to make it easier for tourists to figure out costs (to put it another way -- so that tourists don't have to do the math in their head). My hotel in Dubrovnik quoted rates in Euro, but when it came time to paying, they told me the amount in Kuna and charged my credit card in Kuna.

The kuna is quite stable, it's been hovering at about 7.5 to the euro for a few years now. Quoting accommodation prices in euro is done purely as a courtesy to European tourists. The stability of the kuna vs. the euro actually helps making this double quotation such a widespread phenomenon, as owners don't need to worry about a possible large mismatch between the two quoted prices.

You should always pay in kuna, though. Businesses may accept euros for your convenience, but it may or may not be at a good exchange rate - they pay their taxes, wages and suppliers in kuna, so they definitely won't have the incentive to offer you a better rate than the bank or exchange bureau.

Thanks for the advice.