I know, I know, a cat leash is a ridiculous idea. Cats are too prickly, too willful to endure such pampered indignity. I might as well suggest my cat learn to make a delicious veal parmigiana, or play Bob Dylan songs on the harmonica. In five years of living in New York -- a city that prides itself on its vast parade of human experience -- I've only seen one cat on a leash. (Putting the ratio of strangers' penises to leashed cats at 2:1.) The New York Times wrote about a real estate broker on the Upper West Side who leash trained his cat, which suggests just how remarkable the feat is. Even the phrase "cat on a leash" has a campy spark of the impossible, like something you'd see in a Farrelly brothers movie, or hear about in a novelty song: "Cat on a leash! He don't eat quiche!" But if you start digging a bit into the world of cats on leashes, what you will discover is just how many people have already tried it.
After much angst, Hepola tried a leash on her cat and was surprised by how the adventure turned out. You might not be so surprised. Link
My new cat was harness trained as 10 month old kitten. At first, he hated it. Now he meows excitedly when I pick up his harness and leash. He still spooks easily, which means I have to be very aware of my surroundings. (He hates cars, which I consider a plus.) But when I take him out now, he jogs along the side walk with his tail high in the air. He is familiar with the limitations of the leash and even follows when I call him. He is also clever and I had to add a strap to his harness to stop his Houdini like escapes from it.
Truly depends on the cat and the owner. A lot of leash training a cat involves hours and hours of just letting them get used to it and feel safe with you outside. Some cats will never feel safe enough outside to walk on a harness. Also, you don't walk a cat on a leash so much as follow a cat on a leash or cajole the cat on a leash a few feet this way or that and periodically untangle the leash from various items. It's nothing like walking a dog. Most cats have little interest in following you much less being obedient to 'proper leash etiquette'. A leash just keeps the cat from taking off full speed into traffic or climbing a tree you can't get them out of.