Do rabbits eat lettuce or cabbage?

Rabbits can eat cabbage leaves, but too much is unhealthy for them.

White and light-coloured cabbages should be avoided entirely or else offered sparingly as a treat only -- these varieties are low in nutrients, and can lead to diarrhea and gas.

Dark-coloured cabbage leaves are rich in nutrients but they also cause gas if the rabbit eats too much of them. This is true of all vegetables related to cabbage (i.e. all cruciferous vegetables, including kale, collards, Brussels sprouts, broccoli, cauliflower, rapini/rabe, turnip greens, arugula, watercress, radish greens, many kinds of Chinese greens, etc.). Some rabbits are very sensitive to these vegetables and develop gas easily, and they should avoid all cabbages entirely. Most rabbits benefit from including these veggies in the rotation of their daily "salad" greens, but you should keep track of what you're serving and make sure not to serve too many veggies in this group.

Gas is painful for rabbits and, if not quickly resolved, gas can turn into serious illness (GI stasis). If you have a rabbit, you should learn about the signs and symptoms for gas, and how to treat it -- this way you'll avoid serious illness and expensive vet bills.

See the related questions and links below for more info.