This paper summarizes what we have learned in the past 20 years about canine cognitive abilities, how these abilities change over time, and how canine cognition compares with human cognition. We have developed a battery of objective neuropsychological tasks to assess several cognitive domains. With respect to learning ability, dogs are proficient in tasks requiring associative learning and acquisition of simple relational rules. We’ve also examined performance on several tasks that assess executive function. Dogs perform well on two of these — reversal learning and selective attention — and poorly on others — notably tasks aimed at concept learning. On tasks designed to assess working memory, dogs require extensive training and show erratic performance in visual object recognition, but show much higher levels of performance on tasks assessing visuo spatial memory. Most of our research has used laboratory- housed Beagle dogs. We have now extended this work to the clinic and have obtained similar data from pet dogs. Cognitive abilities change with age in a manner that varies with cognitive domain. Tasks that involve complex learning are more sensitive to age than tasks solved more easily. These findings parallel the kinds of age-dependent cognitive changes that are known to occur in humans. There also are notable individual differences, particularly in performance on specific tasks. Some dogs can be characterized as successful agers, while others show a moderate impairment, which may correspond to a human condition known as mild cognitive impairment (MCI). Still other dogs develop more severe impairment, which may correspond to human dementia. These results model many aspects of human cognition, including the cognitive changes associated with human aging and the development of dementia