Americans love dogs, there’s no doubt about that. It’s estimated that the dog population in the United States is almost 80 million, and that 44% of households have a dog.

We typically get dogs when they’re puppies and form bonds that last a lifetime. It is when they are puppies that our canine friends are at their peak level of cuteness and eagerness for play, and are still a size we can manage. It is at that young age our favorite animal companions are perhaps the most irresistible. While they would perhaps never say it out loud, some dog owners may privately wish their puppy would never grow up.

Dogs are the most adoring pets for many, and puppies are the most adoring and adorable dogs. It’s no surprise that adolescent infatuation is described as puppy love. 24/7 Wall St. set out to identify the breeds that stay puppies the longest. Dogs reach adulthood at different states. But some appear to stay puppies longer than others.

We compiled the list based on a range of factors for which data were available, including life expectancy and size, as well as other more intangible factors such as temperament, playfulness, and cuteness. (These dogs will never make the list.)

Small dogs, especially the toy breeds, are more like puppies even when full grown, while breeds with a strong prey drive or a reputation for fierceness may not seem puppy-like even when young. And being puppy-like may not be compatible with other desirable attributes, such as those looked for in guard and watch dogs.

Click here to see the 20 dogs that stay puppies the longest.