She had a $15,000 Cartier diamond necklace, a $12,000 summer wardrobe, an Escalade and a driver, a full-time nanny, a room and bath of her own, leisurely lunches at the Shore Club, manicures, pedicures, a publicist-everything a party girl could want.

Now Conchita the Chihuahua lives in Gail Posner's $8.3 million, seven-bedroom, eight-bath mansion on a Miami Beach island with her sisters, April Maria the Maltese and Lucia the Yorkshire terrier. After Posner, daughter of corporate raider Victor Posner, died in March and left the bulk of her fortune to her pets, the dogs share the space with Posner's service crew-the maids, bodyguards and personal trainer who inherited millions of dollars and use of the home in exchange for caring for the pooches.

In good times and in bad, Americans love their 77 million dogs, 90 million cats and assorted other domesticated creatures. And while the wealthy might be a tad more cautious with a dollar these days, when it comes to making certain "Spot" is sitting in the lap of luxury-both during and after the life of his owner-it seems that money is no object.

"The last thing I want is for my cats and dogs to be sent to a shelter," says Barbara Monroe, a 74-year-old Sands Point, N.Y., resident who has set aside a $50,000 trust for her pet cats and dogs. "Even though I have four kids, what happens if their children are allergic or move to a place where pets are not allowed? I hope the money set aside might sweeten the pot a little so that I can find a person who will be there for my pets."

Pet trusts are not new, but Posner's will and other cases of furry beneficiaries do point to the fact that some of the nation's wealthiest people view their pets as members of the family-and deserving of special estate-planning treatment.

The late singer Dusty Springfield, for example, had a will that made extensive provisions for her cat Nicholas.  The will instructed that Nicholas' bed be lined with Dusty's nightgown, that Dusty's recordings be played each night at Nicholas' bedtime, and that Nicholas be fed imported baby food.

In another example of puppy love, Doris Duke, the sole heir to Baron Buck Duke, who built Duke University and started the American Tobacco Company, left $100,000 in trust for the benefit of her dog.

Pet trusts have existed in Europe for centuries, but it took until 1990 for the U.S. Uniform Probate Code (UPC) to be changed to allow states to provide for the creation of pet trusts.  Forty-four states have since enacted pet trust laws.  Only Kentucky, Louisiana, Massachusetts, Minnesota, Mississippi and West Virginia do not have laws authorizing pet trusts. Residents in those states, however, can create a trust for a human beneficiary with the stipulation that trust funds should be used for pet care. But such trust provisions are honorary and cannot be legally enforced.

How do you set up a pet trust to withstand a legal challenge? Francis Carlyle, vice chair of the American Bar Association's Animal Law Committee, strongly suggests staying within reason. "I don't allow [clients] to overfund, which would open up to a challenge," Carlyle says. "The crucial point is to not go crazy."

But that's apparently hard advice for some wealthy benefactors to follow when they're crazy about their pets. New York hotel queen Leona Helmsley, who died in 2007, set up perhaps the most famous pet trust of all time. She left $12 million to Trouble, her pet Maltese. The will set off legal battles and death threats against the dog, who would have inherited more than any human member of the family. A judge later reduced the dog's cut to $2 million, ruling that amount would more than adequately cover the cost of Trouble's care. The case was so volatile that Trouble had to be moved to a secret location under an assumed name. The pet's security costs alone ranged between $100,000 and $200,000 per year.