Is a day trip from Rome to Pompeii a good idea or a bad one?

Not sure where you got the idea that it's three hours each way but it's really not. The fast train can get you to Naples in an hour. From there it's a half hour commuter train ride to the ruins so less than 2 hours total if you just miss the commuter train.

I like doing Pompeii as a day trip. The train ride is relaxing and gives you a breather.

I wouldn't do it as an organized trip. Book train tickets from Roma termini to Napoli Centrale. Once at the station just follow the signs and crowds downstairs, buying your commuter tickets along the way.

Tours that include Pompeii and Positano really don't give you enough time in either location to enjoy them. Save Positano for your next trip when you can spend a few days there.

Donna

Did you look at going there by train as it appears to be an hour quicker than driving?

Rome to Naples in 1 hour change to the Campania Express or Circumvesuviana train which stops at Pompeii villa dei misteri station a few yards from the entrance. Positiano is too far with all the Amalfi coast traffic to get there,

We went to the cone of Mt Vesuvius also before venturing to Pompeii

It is very doable as a day trip via train but no way would I drive it for too many reasons to even mention!!

Ditto to the above: if you do it, do it by train on your own. Skip the Amalfi and save it for a future trip when you can give it the time it demands.

Depending on where you stay in Rome and from where you judge your travel time to begin, it can take over three hours to get to Pompei. The moment one steps out of the front door is travel time. Sleeping next to the Termini, coupled with a perfect connection, will help you make decent time. Consider Ostia Antica. If you are keen on renting a car, the Garden of Ninfa beats both for me.

A few additional thoughts. You could do a visit to Herculaneum (Ercolano) instead of Pompeii. It was also devastated by Vesuvius. It’s a little closer to Rome and not as big as Pompeii. Additionally, more was left in situ than at Pompeii. Most of the stuff from Pompeii is in the National Archaeological Museum in Naples. Another substitute for Pompeii might be Ostia Antica. If you want a guide at Pompeii, I believe there are certified guides available at the entrance. This has been true at most of the major sites we’ve visited in Europe and Mexico.

Very easy and doable by high speed train to Napoli Centrale (70 min) then Circumvesuviana commuter train from Napoli Central to Pompei. About a couple of hours each way, door to door, all inclusive. Just be aware the last high speed train back to Rome departs from Napoli Centrale at 7:30pm. After that only slower trains that take twice as long.

I have posted a how-to on a previous thread, but I seem to remember leaving Roma Termini station around 8:30 AM, changing trains at Napoli Centrale, Circumvesuviana to Pompei Scavi exit, visiting the ruins for 2-3 hours, backtrack on the CV to Napoli Centrale, taxi to any one of a number of great Napolitan pizza joints in Naples, taxi back to the station, train back to Roma Termini, arriving around 7:30 PM.

Do it!