Passengers with mobility issues:

Most modern (large) ships have specially-designed cabins for guests using wheelchairs. In general, they have two classifications of cabins:

Modified Cabins: these cabins have been modified from our standard cabins to include wider entry doorways. The cabin entry measures approximately 29". The cabin bathroom entry ranges from 22" to 29", with a lip ranging from 3.5" to 8" into the bathroom. These cabins are reserved for guests who use a wheelchair for distance or guests with limited mobility.

Fully accessible cabins: these cabins have an approximately 32" entry doorway into the cabin and cabin's bathroom. There are no lips into the bathroom. They have roll-in showers with fold-down shower seats. Additionally, there is a full turnaround space of approximately 60" x 60" in the cabin and as well as in cabin's bathroom. These cabins are reserved for guests who use a wheelchair, have limited or no mobility, or guests who use motorized scooters.

In general the larger and newer the ship the more stable it is and in general easier to get around..

Getting on/off the ship:

For transportation from the airport to the pier, Hydraulic Lift Transfer is sometimes available for guests with mobility limitations if requested in advance.

Ports in general use stairs or gangplanks or airport-like jet bridges to move passengers. Depending on the tides these can become very steep and often the lower gangways can not be used.
The lower the tidal difference, the easier it will to get on/off board.
The map below will show you the low (blue) and high (red) around the world:

tides

Areas with no or little tide differences are:
Mediterranean
Baltic Sea including Oslo.
Caribbean

Areas with very high tide differences are:
Normandy France
North East Canada (Bay of Fundy 12 meter!)
Cook Inlet USA
Bristol Channel UK

Check here for low tides expected during your cruise.

Tender Ports:

At a tender port, the ship isn't able to pull up to the pier or dock, usually because it's too shallow. You'll be loaded onto a small vessel called a tender, and taken to shore that way. Sometimes if there are a lot of ships at a regular port, some of the ships may have to stay offshore and bring their passengers in by tender. In general, only collapsible wheelchairs and rollator walkers are accepted.

Tender Ports
Airlie Beach, Australia Ajaccio, Corsica Akaroa, New Zealand Alesund, Norway Bar Harbor, Maine Bay of Islands, New Zealand Belize City, Belize Benoa, Bali, Indonesia Bora Bora, French Polynesia Buzios, Brazil Cabo Frio, Brazil Cairns, Australia Cannes (Monte Carlo), France Champagne Bay, Vanuatu Charlottetown, Prince Edward Island CocoCay, Bahamas Copacabana Beach, Brazil Denarau, Fiji Dubrovnik, Croatia Edinburgh, Scotland	Esperance, Australia La Spezia (Florence/Pisa), Italy Gaspe, Canada Geiranger, Norway George Town, Grand Cayman Geraldton, Australia Hanoi (Halong Bay), Vietnam Honnigsvag, Norway Icy Strait Point, USA Ilha Grande, Brazil Ilhabela, Brazil Isle of Pines, New Caledonia Jeju, Republic of Korea (South Korea) Kailua Kona, Hawaii Ko Samui, Thailand Kotor Montenegro Lahaina (Maui), Hawaii Leknes (Lofoten), Norway Lerwick/shetland, Scotland Lifou, Loyalty Island	Lombok, Indonesia Malacca, Malasia Moorea, French Polynesia Mykonos, Greece Mystery Island, Vanuatu Newport, Rhode Island Villefranche (Nice), France Ouvea (Wadrilla), Loyalty Island Phuket, Thailand Port Douglas, Australia Portobelo, Brazil Punta Del Este, Uruguay Samana, Dominican Republic Santorini, Greece Split, Croatia Sydney, Australia Sydney, Nova Scotia Visby, Sweden

This list is a guide only, sometimes smaller ships are able to dock.

West European and North American cruise ports cities are in general "wheelchair" friendly.

For other health issues consult your agent or cruise line before you book.