i want to leave capri one morning, take the ferry to salerno, hop on a train to pompeii, spend a few hours there and want to head to rome that same evening...
- is this the best way to get from capri to pompeii?
- what is the best way to get from pompeii to rome?
- how long do you think this day's journey will be?
is it worth it to stay overnight in pompeii that night and leave for rome the next morning? if so, what more is there to do in pompeii?

You mean SORRENTO, not SALERNO.
I've not done what you intend to do, but I believe you're on the right track. After your Pompeii visit, you'll train to Naples and then take a 2 hour train ride to Rome.

does anyone know how long the train ride from pompeii to naples is?

http://www.massalubrense.it/circum.htm is the site I found and it looks like 30 minutes +/- from Pompeii to Naples. Remember that you are taking the Circumvesuviana train from Sorrento to Pompeii and changing to the Trenitalia line in Naples. My recollection was that it was about a 10 minute walk from one to the other. Everything is well-marked.

We went through Naples train station a couple of times on a Sicily/Sorrento/Amalfi/Rome trip and every single Italian person we spoke to said to watch for pickpockets at the Naples Train Station. We were soooo alert, it was silly. The station was filled with police and no one was even near us.

We planned a half day in Pompeii and stayed the entire day-it was fascinating to DH and me.

The Circumvesuviana train is in the basement of the Garibaldi or Centrale train station,(same thing)so just go up to the Trenitalia train area and make sure you take Eurostar train (faster), not Intercity. If you stay till closing of Pompeii ruins I suggest you plan to eat dinner in Naples before travelling on to Rome. Google a good Pizza restaurant, Naples is famous for their pizza. You may have time to see a bit of Naples before heading to Rome, check out the HopON HopOff bus, google for more info, buy your ticket when you get on,(don't buy ahead,not necessary) and it will take you all around the city. It starts down at the Piazza Municipo but you can board at any of their stops.

As mentioned above, you want the ferry from Capri to Sorrento, not Salerno. Pompeii Scavi (the train stop you want) is about halfway between Sorrento and Naples. If you have luggage, Pompeii (the ruins, not the train station) has luggage storage (used to be free).

Ciao, I live in Castellamare di Stabia and this town, South on the Gulf of Naples, has a direct ferry link with Capri although you'll call in at Sorrento on the way to C/Mare. Ponpeii is on the outskirts of the town.You could visit this historic location during say 4 hours and return to C/Mare station to catch a train to Rome with a changeover in Naples.
However, Capri and Pompeii in one day is impossible due to the ferry service and time it takes to go and return (approx. 90 mins.)apart from visiting this island. Alternatively you can catch a train from Sorrento as it stops at Pompeii.