When we were in Rovinj last summer, Thomsons offered a day trip to Dubrovnik (mainly to promote the area) which involved a short flight from Pula to Dubrovnik. We didn't go as it was a long day, and we felt we had travelled enough to get there in the first place.

Whether you can find this tour available from local operators, or book flights yourself I don't know. I suspect it is too far to drive in a day?

btw you can also do Venice trip from Rovinj too, and we think Rovinj may be a more picturesque resort than Porec?

Many thanks acorncup for your reply ,as would only be in croatia for a week we might now opt for cavtat(been recommended)as we would love to see dubrovnik & might be too much of a drag from porec