We are staying at Positano and will be travelling by car from there to Rome. Would it be feasible and worthwhile for us to go via Paestum on our way to Rome as we will not have a chance to do it as a daytrip during our short 3 night stay in Positano.
Paestum is south of Salerno, it's not on the way from Positano to Rome. It's probably a two-hour drive south from Positano. It is a very interesting site, basically an unearthed Greek town. They also have a good museum displaying objects they've found. A couple hours is all you need to see the site. If you're interested in Greek temples and ruins and have the extra time, it's worth it.
As Tom said, it's in the opposite direction from Positano, not on the way to Rome. But worth it if you can make the time. Some of the best preserved Greek architecture you'll see anywhere.
You probably want to look at one of the online maps to see its location relative to Positano and to get an estimate of driving time: either Google Map, Google Earth, Bing.com.
Yes Pam it is well worth the time to visit, but it is a hike to get down there (50 mins by train passed Salerno). Plan on giving this attraction the better part of a day to travel to, enjoy, then return to Positano. This spring was our second trip to the Amalfi Coast and the first time we made it to Paestum. The ruins at Paestum are gigantic. Colossal buildings that will really awe strike you. The staff at our hotel in Sorrento was surprised that we took the trip. It's not close to anything. Happy trails!
Absolutely worth it. Amazing temples...very humbling to imagine how they were built. And there is a lovely restaurant on the grounds--while we were there, the manager asked us if we knew Rick Steve!
You might want to check out the organic buffalo mozarella farm nearby. These water buffalo line up for massages and make their way to an automatic milking device anytime they want to, as long as it is twice a day --doesn't matter when. The mozarella sells out by 10am since they make it fresh every day. Very interesting. And we all test tasted afterwards...yum. Enjoy your trip!
If you go to Paestum you will see the ONLY non-reconstructed Greek temples in mainland Italy. I did a little research on this. They appear to be the only ones. These structures were Free Standing when they were "rediscovered" in the 1700's. You'll see them as they were built and not something pieced back together from parts found scattered in the ground. Near everything else you'll see in mainland Italy, including parts of Pompeii and Ostia Antica are 19th century recreations built as close as they thought they could above the dirt that once covered them.