I am going on Mediterranean cruise leaving 9/18 for 12 days..board in Venice and end in Barcelona. Will be taking many shore excursions...Need help in what to pack...

Remember it is summer time, and it could get really hot and humid in the countries you are visiting. During the day and excursions, nice shorts, t- shirts and sneakers will do it. You can still look nice and clean in summer clothes. For the evening, sure you want to look great. Formal nights, I do think some people overdress, but still look nice. If male, a suit will do, females , a nice cocktail dress.
Non formal nights, nice casual clothes, no shorts or jeans. Just pretend you are at home and going out to a very nice restaurant to celebrate a special occasion, how would you dress???

remember to wear something that covers your knees and shoulders on your excursions to Italy. Otherwise, you will not be allowed to go in the churches

And do pack in layers. The evenings on the ship, outdoors and even in air-conditioned lounges are chilly. I always seem to need a wrap. Don't know if September will be like late May, but I was very glad that I had the fleece and wind-brealer on an evening tour in Rome.

I wish I was going too. What a rich experience you're in for!

Good luck with the packing - we're struggling with the very same issue. We are on the Celebrity cruise before yours (Barcelona to Venice)...with 3 formal nights as well as the various recommended dress codes for the shore excursions, it can get a little overwhelming.