Mediterranean cruises cover a vast array of ports in several countries. For a cruise with so many possibilities, it's a good idea to pack with those options in mind. Think about the kinds of activities you will want to participate in on your vacation -- swimming at the beach or visiting the Vatican -- and pack accordingly.
Being comfortable is a top priority during your cruise vacation -- casual wear is the standard daytime attire for most cruises. Bring a few different options in footwear, including low-heeled or rubber-heeled shoes for walking on deck, sandals for beach excursions and a pair of dressier shoes for formal dining. Check the ship's dress codes for options suitable for nighttime.
It's a good idea to check local weather before boarding and bring a few safeguards, such as an umbrella if you travel during the wet season and a light jacket or a sweater for cooler nights.
Many churches and cathedrals in Europe require some degree of modest attire for visitors. You may not be permitted to enter if wearing "too short" shorts, and women may be asked to cover bare shoulders (it's a good idea to tuck a lightweight scarf into your purse or tote). Comfortable, broken-in walking shoes are best for navigating the uneven, cobblestoned streets found in the historic districts of many European cities.
Remember to pack all your medications, prescription or otherwise, in a bag you can carry onto your flights. A hat, sunglasses and sunscreen are all necessities for sunny days on the ship and ashore.