I'm planning a trip to Croatia next summer and want to rent a house. Probably in the Split area or Istrian Peninsula. Should I use VRBO or a Real Estate Agent? If an agent, can anybody make a recommendation for each area?

Why just VRBO? I've never used the site as early on in the online rental game I chose Airbnb because there were more units & there were more less expensive options. I've continued & with rare exception have been satisfied. So I suggest you have a look at more sites than 1, there will be more possibilities than you can imagine.

That is good advice, and I always check both sites. I only used VRBO because I want to know whether to use those sites or a realtor.

I participated in a very long thread here during the last year documenting fraudulent listings on HomeAway. VRBO is a sister company, and they really are the same thing. Make sure you book within their system, although that will only protect your payment NOT the inconvenience of potentially finding as you arrive that the place doesn't exist. Despite some obvious fake listings I pointed to, HomeAway continued to post them, and they seemed to show little care about them. They even collected a currency exchange fee from a poster here despite the listing being fake and refused to make the poster whole. I have had good luck many, many times with Airbnb. Try to stick with listings at either company that have a history of reviews. That is often the sign that it is legit. Realtors tend to have listings that are more expensive, since their fees can be a lot more than an online listing agency.

Using a real estate agency to rent a house in Europe these days seems like a strange, very old-fashioned option to me. Why, when there are so very many other, less expensive options? I don't know about Croatia, but here in France a real estate agency would be about the last place you'd go for a short-term rental -they deal mostly with permanent or semi-permanent occupants.

I probably wouldn't use VRBO or HOMEAWAY, either. I'd go to booking.com and then check AirBnb.You can also contact the tourist offices in whichever places interest you - they keep lists of local people with rental offerings.