The Cairn Terrier is a small terrier type dog that has more of the personality and instinctive drives of a hunting dog than it does of a terrier. In the original countryside where the Cairn was found, the Highlands of Scotland, this was the breed of choice for hunting the fox, the badger and the otter. Terriers with this sort of drive are often termed "sporting terriers".

The Cairn terrier of modern times can be found in many colors. The only "forbidden" color is white. Back when the Cairn was developed, the white coloring split off into a separate breeding that later became known as the West Highland White Terrier. Any Cairn that is born a solid white is a "throwback" to this part of the bloodline and to keep the "Westy" pure, a white Cairn may not be shown and any offspring would not be registerable.

The Cairn is generally healthy but there presently exists a condition called Legg Perthes, a condition seen in other small breeds also. Legg Perthes is a malformation of the hip that can be identified with x-rays. It causes pain to the animal. In another bone-related disease, the Cairn suffers occasionally from luxation of the patella, or kneecap, which is similar to the subluxation of the hip found in hip dysplasia in larger breeds. Another inherited condition in which the jaw becomes malformed as the puppy grows is also prevalent. This condition is called "lion jaw" and again causes pain and also prevents the dog from eating naturally. It goes without saying that any dogs afflicted with these conditions should never be used in the breeding program. Some of these bone related problems can be detected with x-rays and this is a useful tool for the serious breeder. All x-rays can be sent to the Orthopedic Foundation of American (OFA) and to similar organizations in other countries, where the x-rays are "graded" by qualified veterinarians and the resulting decision helps to determine the extent to which these bone conditions are present.

The Cairn is a popular terrier breed on both sides of the Atlantic. It often has one of the highest entries at the annual Montgomery County All Terrier show held in Montgomery County, Pennsylvania every October. It is a great family pet but its history as a "sporting terrier" defines it's personality. It is the sort of dog that will not take no for an answer, whether it be in it's reaction to another dog or in its desire to accomplish something other than what it's master wishes! It is excellent with children, being plucky and ready to go. It is happy to live in a single dog household but owners shouldn't want to leave this little dog in a fenced in area without supervision, for he is quite capable of digging himself out of a grass or dirt area. The Cairn has shown himself to be a popular entry in the "Go to Ground" Trials of terriers as well as competing in Obedience and Agility trials.